{"id":271,"date":"2024-04-26T11:15:33","date_gmt":"2024-04-26T03:15:33","guid":{"rendered":"https:\/\/www.vanforever.com.cn\/?p=271"},"modified":"2024-05-22T19:07:07","modified_gmt":"2024-05-22T11:07:07","slug":"%e9%80%9f%e5%ad%a6mysql%e5%9f%ba%e7%a1%80%e7%94%a8%e6%b3%95","status":"publish","type":"post","link":"https:\/\/www.vanforever.com.cn\/?p=271","title":{"rendered":"\u901f\u5b66MySQL\u57fa\u7840\u7528\u6cd5"},"content":{"rendered":"<div  class='collapse-block shadow-sm collapse-block-transparent collapsed hide-border-left'><div class='collapse-block-title'><span class='collapse-block-title-inner'>\u67e5\u770b\u7279\u8272\u56fe\u7247<\/span><i class='collapse-icon fa fa-angle-down'><\/i><\/div><div class='collapse-block-body' style='display:none;'><div class='fancybox-wrapper lazyload-container-unload' data-fancybox='post-images' href='https:\/\/pic.vanforever.com.cn\/Vanforever\/20240421\/wallhaven-3lerw3_3840x2400.png'><img class=\"lazyload lazyload-style-1\" src=\"data:image\/svg+xml;base64,PCEtLUFyZ29uTG9hZGluZy0tPgo8c3ZnIHdpZHRoPSIxIiBoZWlnaHQ9IjEiIHhtbG5zPSJodHRwOi8vd3d3LnczLm9yZy8yMDAwL3N2ZyIgc3Ryb2tlPSIjZmZmZmZmMDAiPjxnPjwvZz4KPC9zdmc+\"  loading=\"lazy\" decoding=\"async\" class=\"alignnone size-large\" data-original=\"https:\/\/pic.vanforever.com.cn\/Vanforever\/20240421\/wallhaven-3lerw3_3840x2400.png\" src=\"data:image\/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsQAAA7EAZUrDhsAAAANSURBVBhXYzh8+PB\/AAffA0nNPuCLAAAAAElFTkSuQmCC\" width=\"3840\" height=\"2400\" \/><\/div><\/div><\/div>\n<h2 id=\"sql-select-\u8bed\u53e5\">SQL SELECT \u8bed\u53e5<\/h2>\n<p>SELECT \u8bed\u53e5\u7528\u4e8e\u4ece\u6570\u636e\u5e93\u4e2d\u9009\u53d6\u6570\u636e\u3002<\/p>\n<p>\u7ed3\u679c\u88ab\u5b58\u50a8\u5728\u4e00\u4e2a\u7ed3\u679c\u8868\u4e2d\uff0c\u79f0\u4e3a\u7ed3\u679c\u96c6\u3002<\/p>\n<h3 id=\"sql-select-\u8bed\u6cd5\">SQL SELECT \u8bed\u6cd5<\/h3>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT column1, column2, ...\nFROM table_name;\n<\/code><\/pre>\n<p>\u4e0e<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT * FROM table_name;\n<\/code><\/pre>\n<p><strong>\u53c2\u6570\u8bf4\u660e\uff1a<\/strong><\/p>\n<ul>\n<li><strong>column1, column2, &#8230;<\/strong>\uff1a\u8981\u9009\u62e9\u7684\u5b57\u6bb5\u540d\u79f0\uff0c\u53ef\u4ee5\u4e3a\u591a\u4e2a\u5b57\u6bb5\u3002\u5982\u679c\u4e0d\u6307\u5b9a\u5b57\u6bb5\u540d\u79f0\uff0c\u5219\u4f1a\u9009\u62e9\u6240\u6709\u5b57\u6bb5\u3002<\/li>\n<li><strong>table_name<\/strong>\uff1a\u8981\u67e5\u8be2\u7684\u8868\u540d\u79f0\u3002<\/li>\n<\/ul>\n<hr \/>\n<h2 id=\"sql-select-distinct-\u8bed\u53e5\">SQL SELECT DISTINCT \u8bed\u53e5<\/h2>\n<p>\u5728\u8868\u4e2d\uff0c\u4e00\u4e2a\u5217\u53ef\u80fd\u4f1a\u5305\u542b\u591a\u4e2a\u91cd\u590d\u503c\uff0c\u6709\u65f6\u60a8\u4e5f\u8bb8\u5e0c\u671b\u4ec5\u4ec5\u5217\u51fa\u4e0d\u540c\uff08distinct\uff09\u7684\u503c\u3002<\/p>\n<p>DISTINCT \u5173\u952e\u8bcd\u7528\u4e8e\u8fd4\u56de\u552f\u4e00\u4e0d\u540c\u7684\u503c\u3002<\/p>\n<h3 id=\"sql-select-distinct-\u8bed\u6cd5\">SQL SELECT DISTINCT \u8bed\u6cd5<\/h3>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT DISTINCT column1, column2, ...\nFROM table_name;\n<\/code><\/pre>\n<p><strong>\u53c2\u6570\u8bf4\u660e\uff1a<\/strong><\/p>\n<ul>\n<li><strong>column1, column2, &#8230;<\/strong>\uff1a\u8981\u9009\u62e9\u7684\u5b57\u6bb5\u540d\u79f0\uff0c\u53ef\u4ee5\u4e3a\u591a\u4e2a\u5b57\u6bb5\u3002\u5982\u679c\u4e0d\u6307\u5b9a\u5b57\u6bb5\u540d\u79f0\uff0c\u5219\u4f1a\u9009\u62e9\u6240\u6709\u5b57\u6bb5\u3002<\/li>\n<li><strong>table_name<\/strong>\uff1a\u8981\u67e5\u8be2\u7684\u8868\u540d\u79f0\u3002<\/li>\n<\/ul>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u4ec5\u4ece &#8220;Websites&#8221; \u8868\u7684 &#8220;country&#8221; \u5217\u4e2d\u9009\u53d6\u552f\u4e00\u4e0d\u540c\u7684\u503c\uff0c\u4e5f\u5c31\u662f\u53bb\u6389 &#8220;country&#8221; \u5217\u91cd\u590d\u503c\uff1a<\/p>\n<h4 id=\"\u5b9e\u4f8b\">\u5b9e\u4f8b<\/h4>\n<pre><code>SELECT DISTINCT country FROM Websites;\n<\/code><\/pre>\n<hr \/>\n<h2 id=\"sql-where-\u5b50\u53e5\">SQL WHERE \u5b50\u53e5<\/h2>\n<p>WHERE \u5b50\u53e5\u7528\u4e8e\u63d0\u53d6\u90a3\u4e9b\u6ee1\u8db3\u6307\u5b9a\u6761\u4ef6\u7684\u8bb0\u5f55\u3002<\/p>\n<h3 id=\"sql-where-\u8bed\u6cd5\">SQL WHERE \u8bed\u6cd5<\/h3>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT column1, column2, ...\nFROM table_name\nWHERE condition;\n<\/code><\/pre>\n<p>\u53c2\u6570\u8bf4\u660e\uff1a<\/p>\n<ul>\n<li><strong>column1, column2, &#8230;<\/strong>\uff1a\u8981\u9009\u62e9\u7684\u5b57\u6bb5\u540d\u79f0\uff0c\u53ef\u4ee5\u4e3a\u591a\u4e2a\u5b57\u6bb5\u3002\u5982\u679c\u4e0d\u6307\u5b9a\u5b57\u6bb5\u540d\u79f0\uff0c\u5219\u4f1a\u9009\u62e9\u6240\u6709\u5b57\u6bb5\u3002<\/li>\n<li><strong>table_name<\/strong>\uff1a\u8981\u67e5\u8be2\u7684\u8868\u540d\u79f0\u3002<\/li>\n<\/ul>\n<h3 id=\"where-\u5b50\u53e5\u4e2d\u7684\u8fd0\u7b97\u7b26\">WHERE \u5b50\u53e5\u4e2d\u7684\u8fd0\u7b97\u7b26<\/h3>\n<p>\u4e0b\u9762\u7684\u8fd0\u7b97\u7b26\u53ef\u4ee5\u5728 WHERE \u5b50\u53e5\u4e2d\u4f7f\u7528\uff1a<\/p>\n<figure class=\"table-figure\">\n<table>\n<thead>\n<tr>\n<th style=\"text-align: left;\">\u8fd0\u7b97\u7b26<\/th>\n<th style=\"text-align: left;\">\u63cf\u8ff0<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td style=\"text-align: left;\">=<\/td>\n<td style=\"text-align: left;\">\u7b49\u4e8e<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">&lt;&gt;<\/td>\n<td style=\"text-align: left;\">\u4e0d\u7b49\u4e8e\u3002<strong>\u6ce8\u91ca\uff1a<\/strong>\u5728 SQL \u7684\u4e00\u4e9b\u7248\u672c\u4e2d\uff0c\u8be5\u64cd\u4f5c\u7b26\u53ef\u88ab\u5199\u6210 !=<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">&gt;<\/td>\n<td style=\"text-align: left;\">\u5927\u4e8e<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">&lt;<\/td>\n<td style=\"text-align: left;\">\u5c0f\u4e8e<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">&gt;=<\/td>\n<td style=\"text-align: left;\">\u5927\u4e8e\u7b49\u4e8e<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">&lt;=<\/td>\n<td style=\"text-align: left;\">\u5c0f\u4e8e\u7b49\u4e8e<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">BETWEEN<\/td>\n<td style=\"text-align: left;\">\u5728\u67d0\u4e2a\u8303\u56f4\u5185<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">LIKE<\/td>\n<td style=\"text-align: left;\">\u641c\u7d22\u67d0\u79cd\u6a21\u5f0f<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">IN<\/td>\n<td style=\"text-align: left;\">\u6307\u5b9a\u9488\u5bf9\u67d0\u4e2a\u5217\u7684\u591a\u4e2a\u53ef\u80fd\u503c<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<hr \/>\n<h2 id=\"sql-and--or-\u8fd0\u7b97\u7b26\">SQL AND &amp; OR \u8fd0\u7b97\u7b26<\/h2>\n<p>\u5982\u679c\u7b2c\u4e00\u4e2a\u6761\u4ef6\u548c\u7b2c\u4e8c\u4e2a\u6761\u4ef6\u90fd\u6210\u7acb\uff0c\u5219 AND \u8fd0\u7b97\u7b26\u663e\u793a\u4e00\u6761\u8bb0\u5f55\u3002<\/p>\n<p>\u5982\u679c\u7b2c\u4e00\u4e2a\u6761\u4ef6\u548c\u7b2c\u4e8c\u4e2a\u6761\u4ef6\u4e2d\u53ea\u8981\u6709\u4e00\u4e2a\u6210\u7acb\uff0c\u5219 OR \u8fd0\u7b97\u7b26\u663e\u793a\u4e00\u6761\u8bb0\u5f55\u3002<\/p>\n<h3 id=\"and-\u8fd0\u7b97\u7b26\u5b9e\u4f8b\">AND \u8fd0\u7b97\u7b26\u5b9e\u4f8b<\/h3>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u4ece &#8220;Websites&#8221; \u8868\u4e2d\u9009\u53d6\u56fd\u5bb6\u4e3a &#8220;CN&#8221; \u4e14alexa\u6392\u540d\u5927\u4e8e &#8220;50&#8221; \u7684\u6240\u6709\u7f51\u7ad9\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT * FROM Websites \nWHERE country='CN' \nAND alexa &gt; 50;\n<\/code><\/pre>\n<h3 id=\"or-\u8fd0\u7b97\u7b26\u5b9e\u4f8b\">OR \u8fd0\u7b97\u7b26\u5b9e\u4f8b<\/h3>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u4ece &#8220;Websites&#8221; \u8868\u4e2d\u9009\u53d6\u56fd\u5bb6\u4e3a &#8220;USA&#8221; \u6216\u8005 &#8220;CN&#8221; \u7684\u6240\u6709\u5ba2\u6237\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT * FROM Websites \nWHERE country='USA' \nOR country='CN';\n<\/code><\/pre>\n<h3 id=\"\u7ed3\u5408-and--or\">\u7ed3\u5408 AND &amp; OR<\/h3>\n<p>\u60a8\u4e5f\u53ef\u4ee5\u628a AND \u548c OR \u7ed3\u5408\u8d77\u6765\uff08\u4f7f\u7528\u5706\u62ec\u53f7\u6765\u7ec4\u6210\u590d\u6742\u7684\u8868\u8fbe\u5f0f\uff09\u3002<\/p>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u4ece &#8220;Websites&#8221; \u8868\u4e2d\u9009\u53d6 alexa \u6392\u540d\u5927\u4e8e &#8220;15&#8221; \u4e14\u56fd\u5bb6\u4e3a &#8220;CN&#8221; \u6216 &#8220;USA&#8221; \u7684\u6240\u6709\u7f51\u7ad9\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT * FROM Websites \nWHERE alexa &gt; 15 \nAND (country='CN' OR country='USA');\n<\/code><\/pre>\n<hr \/>\n<h2 id=\"sql-order-by-\u5173\u952e\u5b57\">SQL ORDER BY \u5173\u952e\u5b57<\/h2>\n<p>ORDER BY \u5173\u952e\u5b57\u7528\u4e8e\u5bf9\u7ed3\u679c\u96c6\u6309\u7167\u4e00\u4e2a\u5217\u6216\u8005\u591a\u4e2a\u5217\u8fdb\u884c\u6392\u5e8f\u3002<\/p>\n<p>ORDER BY \u5173\u952e\u5b57\u9ed8\u8ba4\u6309\u7167\u5347\u5e8f\u5bf9\u8bb0\u5f55\u8fdb\u884c\u6392\u5e8f\u3002\u5982\u679c\u9700\u8981\u6309\u7167\u964d\u5e8f\u5bf9\u8bb0\u5f55\u8fdb\u884c\u6392\u5e8f\uff0c\u60a8\u53ef\u4ee5\u4f7f\u7528 DESC \u5173\u952e\u5b57\u3002<\/p>\n<h3 id=\"sql-order-by-\u8bed\u6cd5\">SQL ORDER BY \u8bed\u6cd5<\/h3>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT column1, column2, ...\nFROM table_name\nORDER BY column1, column2, ... ASC|DESC;\n<\/code><\/pre>\n<ul>\n<li><strong>column1, column2, &#8230;<\/strong>\uff1a\u8981\u6392\u5e8f\u7684\u5b57\u6bb5\u540d\u79f0\uff0c\u53ef\u4ee5\u4e3a\u591a\u4e2a\u5b57\u6bb5\u3002<\/li>\n<li><strong>ASC<\/strong>\uff1a\u8868\u793a\u6309\u5347\u5e8f\u6392\u5e8f\u3002<\/li>\n<li><strong>DESC<\/strong>\uff1a\u8868\u793a\u6309\u964d\u5e8f\u6392\u5e8f\u3002<\/li>\n<\/ul>\n<h3 id=\"order-by-\u5b9e\u4f8b\">ORDER BY \u5b9e\u4f8b<\/h3>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u4ece &#8220;Websites&#8221; \u8868\u4e2d\u9009\u53d6\u6240\u6709\u7f51\u7ad9\uff0c\u5e76\u6309\u7167 &#8220;alexa&#8221; \u5217\u6392\u5e8f\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT * FROM Websites \nORDER BY alexa;\n<\/code><\/pre>\n<h3 id=\"order-by-desc-\u5b9e\u4f8b\">ORDER BY DESC \u5b9e\u4f8b<\/h3>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u4ece &#8220;Websites&#8221; \u8868\u4e2d\u9009\u53d6\u6240\u6709\u7f51\u7ad9\uff0c\u5e76\u6309\u7167 &#8220;alexa&#8221; \u5217\u964d\u5e8f\u6392\u5e8f\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT * FROM Websites \nORDER BY alexa DESC;\n<\/code><\/pre>\n<h3 id=\"order-by-\u591a\u5217\">ORDER BY \u591a\u5217<\/h3>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u4ece &#8220;Websites&#8221; \u8868\u4e2d\u9009\u53d6\u6240\u6709\u7f51\u7ad9\uff0c\u5e76\u6309\u7167 &#8220;country&#8221; \u548c &#8220;alexa&#8221; \u5217\u6392\u5e8f\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT * FROM Websites \nORDER BY country,alexa;\n<\/code><\/pre>\n<hr \/>\n<h2 id=\"sql-insert-into-\u8bed\u53e5\">SQL INSERT INTO \u8bed\u53e5<\/h2>\n<p>INSERT INTO \u8bed\u53e5\u7528\u4e8e\u5411\u8868\u4e2d\u63d2\u5165\u65b0\u8bb0\u5f55\u3002<\/p>\n<h3 id=\"sql-insert-into-\u8bed\u6cd5\">SQL INSERT INTO \u8bed\u6cd5<\/h3>\n<p>INSERT INTO \u8bed\u53e5\u53ef\u4ee5\u6709\u4e24\u79cd\u7f16\u5199\u5f62\u5f0f\u3002<\/p>\n<p>\u7b2c\u4e00\u79cd\u5f62\u5f0f\u65e0\u9700\u6307\u5b9a\u8981\u63d2\u5165\u6570\u636e\u7684\u5217\u540d\uff0c\u53ea\u9700\u63d0\u4f9b\u88ab\u63d2\u5165\u7684\u503c\u5373\u53ef\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">INSERT INTO table_name\nVALUES (value1,value2,value3,...);\n<\/code><\/pre>\n<p>\u7b2c\u4e8c\u79cd\u5f62\u5f0f\u9700\u8981\u6307\u5b9a\u5217\u540d\u53ca\u88ab\u63d2\u5165\u7684\u503c\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">INSERT INTO table_name (column1,column2,column3,...)\nVALUES (value1,value2,value3,...);\n<\/code><\/pre>\n<p><strong>\u53c2\u6570\u8bf4\u660e\uff1a<\/strong><\/p>\n<ul>\n<li><strong>table_name<\/strong>\uff1a\u9700\u8981\u63d2\u5165\u65b0\u8bb0\u5f55\u7684\u8868\u540d\u3002<\/li>\n<li><strong>column1, column2, &#8230;<\/strong>\uff1a\u9700\u8981\u63d2\u5165\u7684\u5b57\u6bb5\u540d\u3002<\/li>\n<li><strong>value1, value2, &#8230;<\/strong>\uff1a\u9700\u8981\u63d2\u5165\u7684\u5b57\u6bb5\u503c\u3002<\/li>\n<\/ul>\n<h3 id=\"insert-into-\u5b9e\u4f8b\">INSERT INTO \u5b9e\u4f8b<\/h3>\n<p>\u5047\u8bbe\u6211\u4eec\u8981\u5411 &#8220;Websites&#8221; \u8868\u4e2d\u63d2\u5165\u4e00\u4e2a\u65b0\u884c\u3002<\/p>\n<p>\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u4e0b\u9762\u7684 SQL \u8bed\u53e5\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">INSERT INTO Websites (name, url, alexa, country) \nVALUES ('\u767e\u5ea6','https:\/\/www.vanforever.com\/','4','CN');\n<\/code><\/pre>\n<h3 id=\"\u5728\u6307\u5b9a\u7684\u5217\u63d2\u5165\u6570\u636e\">\u5728\u6307\u5b9a\u7684\u5217\u63d2\u5165\u6570\u636e<\/h3>\n<p>\u6211\u4eec\u4e5f\u53ef\u4ee5\u5728\u6307\u5b9a\u7684\u5217\u63d2\u5165\u6570\u636e\u3002<\/p>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u5c06\u63d2\u5165\u4e00\u4e2a\u65b0\u884c\uff0c\u4f46\u662f\u53ea\u5728 &#8220;name&#8221;\u3001&#8221;url&#8221; \u548c &#8220;country&#8221; \u5217\u63d2\u5165\u6570\u636e\uff08id \u5b57\u6bb5\u4f1a\u81ea\u52a8\u66f4\u65b0\uff09\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">INSERT INTO Websites (name, url, country) \nVALUES ('stackoverflow', 'http:\/\/stackoverflow.com\/', 'IND');\n<\/code><\/pre>\n<hr \/>\n<h2 id=\"sql-update-\u8bed\u53e5\">SQL UPDATE \u8bed\u53e5<\/h2>\n<p>UPDATE \u8bed\u53e5\u7528\u4e8e\u66f4\u65b0\u8868\u4e2d\u5df2\u5b58\u5728\u7684\u8bb0\u5f55\u3002<\/p>\n<h3 id=\"sql-update-\u8bed\u6cd5\">SQL UPDATE \u8bed\u6cd5<\/h3>\n<pre><code class=\"language-mysql\" lang=\"mysql\">UPDATE table_name\nSET column1 = value1, column2 = value2, ...\nWHERE condition;\n<\/code><\/pre>\n<p>\u53c2\u6570\u8bf4\u660e\uff1a<\/p>\n<ul>\n<li><strong>table_name<\/strong>\uff1a\u8981\u4fee\u6539\u7684\u8868\u540d\u79f0\u3002<\/li>\n<li><strong>column1, column2, &#8230;<\/strong>\uff1a\u8981\u4fee\u6539\u7684\u5b57\u6bb5\u540d\u79f0\uff0c\u53ef\u4ee5\u4e3a\u591a\u4e2a\u5b57\u6bb5\u3002<\/li>\n<li><strong>value1, value2, &#8230;<\/strong>\uff1a\u8981\u4fee\u6539\u7684\u503c\uff0c\u53ef\u4ee5\u4e3a\u591a\u4e2a\u503c\u3002<\/li>\n<li><strong>condition<\/strong>\uff1a\u4fee\u6539\u6761\u4ef6\uff0c\u7528\u4e8e\u6307\u5b9a\u54ea\u4e9b\u6570\u636e\u8981\u4fee\u6539\u3002<\/li>\n<\/ul>\n<h3 id=\"sql-update-\u5b9e\u4f8b\">SQL UPDATE \u5b9e\u4f8b<\/h3>\n<p>\u5047\u8bbe\u6211\u4eec\u8981\u628a &#8220;NIIT\u6559\u7a0b&#8221; \u7684 alexa \u6392\u540d\u66f4\u65b0\u4e3a 5000\uff0ccountry \u6539\u4e3a USA\u3002<\/p>\n<p>\u6211\u4eec\u4f7f\u7528\u4e0b\u9762\u7684 SQL \u8bed\u53e5\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">UPDATE Websites  SET alexa='5000', country='USA'  \nWHERE name='NIIT\u6559\u7a0b';\n<\/code><\/pre>\n<h3 id=\"update-\u8b66\u544a\">Update \u8b66\u544a\uff01<\/h3>\n<p>\u5728\u66f4\u65b0\u8bb0\u5f55\u65f6\u8981\u683c\u5916\u5c0f\u5fc3\uff01\u5728\u4e0a\u9762\u7684\u5b9e\u4f8b\u4e2d\uff0c\u5982\u679c\u6211\u4eec\u7701\u7565\u4e86 WHERE \u5b50\u53e5\uff0c\u5982\u4e0b\u6240\u793a\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">UPDATE Websites\nSET alexa='5000', country='USA'\n<\/code><\/pre>\n<p>\u6267\u884c\u4ee5\u4e0a\u4ee3\u7801\u4f1a\u5c06 Websites \u8868\u4e2d\u6240\u6709\u6570\u636e\u7684 alexa \u6539\u4e3a 5000\uff0ccountry \u6539\u4e3a USA\u3002<\/p>\n<p>\u6267\u884c\u6ca1\u6709 WHERE \u5b50\u53e5\u7684 UPDATE \u8981\u614e\u91cd\uff0c\u518d\u614e\u91cd\u3002<\/p>\n<hr \/>\n<h2 id=\"sql-delete-\u8bed\u53e5\">SQL DELETE \u8bed\u53e5<\/h2>\n<p>DELETE \u8bed\u53e5\u7528\u4e8e\u5220\u9664\u8868\u4e2d\u7684\u884c\u3002<\/p>\n<h3 id=\"sql-delete-\u8bed\u6cd5\">SQL DELETE \u8bed\u6cd5<\/h3>\n<pre><code class=\"language-mysql\" lang=\"mysql\">DELETE FROM table_name\nWHERE condition;\n<\/code><\/pre>\n<p>\u53c2\u6570\u8bf4\u660e\uff1a<\/p>\n<ul>\n<li><strong>table_name<\/strong>\uff1a\u8981\u5220\u9664\u7684\u8868\u540d\u79f0\u3002<\/li>\n<li><strong>condition<\/strong>\uff1a\u5220\u9664\u6761\u4ef6\uff0c\u7528\u4e8e\u6307\u5b9a\u54ea\u4e9b\u6570\u636e\u8981\u5220\u9664\u3002<\/li>\n<\/ul>\n<h3 id=\"sql-delete-\u5b9e\u4f8b\">SQL DELETE \u5b9e\u4f8b<\/h3>\n<p>\u5047\u8bbe\u6211\u4eec\u8981\u4ece &#8220;Websites&#8221; \u8868\u4e2d\u5220\u9664\u7f51\u7ad9\u540d\u4e3a &#8220;Facebook&#8221; \u4e14\u56fd\u5bb6\u4e3a USA \u7684\u7f51\u7ad9\u3002<\/p>\n<p>\u6211\u4eec\u4f7f\u7528\u4e0b\u9762\u7684 SQL \u8bed\u53e5\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">DELETE FROM Websites \nWHERE name='Facebook' \nAND country='USA';\n<\/code><\/pre>\n<hr \/>\n<h2 id=\"sql-select-top-\u5b50\u53e5\">SQL SELECT TOP \u5b50\u53e5<\/h2>\n<p>SELECT TOP \u5b50\u53e5\u7528\u4e8e\u89c4\u5b9a\u8981\u8fd4\u56de\u7684\u8bb0\u5f55\u7684\u6570\u76ee\u3002<\/p>\n<p>SELECT TOP \u5b50\u53e5\u5bf9\u4e8e\u62e5\u6709\u6570\u5343\u6761\u8bb0\u5f55\u7684\u5927\u578b\u8868\u6765\u8bf4\uff0c\u662f\u975e\u5e38\u6709\u7528\u7684\u3002<\/p>\n<h3 id=\"mysql-\u8bed\u6cd5\">MySQL \u8bed\u6cd5<\/h3>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT column_name(s)\nFROM table_name\nLIMIT number;\n<\/code><\/pre>\n<h3 id=\"mysql-select-limit-\u5b9e\u4f8b\">MySQL SELECT LIMIT \u5b9e\u4f8b<\/h3>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u4ece &#8220;Websites&#8221; \u8868\u4e2d\u9009\u53d6\u5934\u4e24\u6761\u8bb0\u5f55\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT * FROM Websites \nLIMIT 2;\n<\/code><\/pre>\n<h3 id=\"sql-select-top-percent-\u5b9e\u4f8b\">SQL SELECT TOP PERCENT \u5b9e\u4f8b<\/h3>\n<p>\u5728 Microsoft SQL Server \u4e2d\u8fd8\u53ef\u4ee5\u4f7f\u7528\u767e\u5206\u6bd4\u4f5c\u4e3a\u53c2\u6570\u3002<\/p>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u4ece websites \u8868\u4e2d\u9009\u53d6\u524d\u9762\u767e\u5206\u4e4b 50 \u7684\u8bb0\u5f55\uff1a<\/p>\n<p>\u4ee5\u4e0b\u64cd\u4f5c\u5728 Microsoft SQL Server \u6570\u636e\u5e93\u4e2d\u53ef\u6267\u884c\u3002<\/p>\n<pre><code class=\"language-sql\" lang=\"sql\">SELECT TOP 50 PERCENT * FROM Websites;\n<\/code><\/pre>\n<p><strong>\u6ce8\u610f:<\/strong>\u5728mysql\u4e2d<strong>\u4e0d\u652f\u6301top\u5173\u952e\u5b57<\/strong>\uff0c\u800c\u91c7\u7528limit\u5173\u952e\u5b57\u8fdb\u884c\u4ee3\u66ff<\/p>\n<hr \/>\n<h2 id=\"sql-like-\u64cd\u4f5c\u7b26\">SQL LIKE \u64cd\u4f5c\u7b26<\/h2>\n<p>LIKE \u64cd\u4f5c\u7b26\u7528\u4e8e\u5728 WHERE \u5b50\u53e5\u4e2d\u641c\u7d22\u5217\u4e2d\u7684\u6307\u5b9a\u6a21\u5f0f\u3002<\/p>\n<h3 id=\"sql-like-\u8bed\u6cd5\">SQL LIKE \u8bed\u6cd5<\/h3>\n<pre><code>SELECT column1, column2, ...\nFROM table_name\nWHERE column LIKE pattern;\n<\/code><\/pre>\n<p>\u53c2\u6570\u8bf4\u660e\uff1a<\/p>\n<ul>\n<li><strong>column1, column2, &#8230;<\/strong>\uff1a\u8981\u9009\u62e9\u7684\u5b57\u6bb5\u540d\u79f0\uff0c\u53ef\u4ee5\u4e3a\u591a\u4e2a\u5b57\u6bb5\u3002\u5982\u679c\u4e0d\u6307\u5b9a\u5b57\u6bb5\u540d\u79f0\uff0c\u5219\u4f1a\u9009\u62e9\u6240\u6709\u5b57\u6bb5\u3002<\/li>\n<li><strong>table_name<\/strong>\uff1a\u8981\u67e5\u8be2\u7684\u8868\u540d\u79f0\u3002<\/li>\n<li><strong>column<\/strong>\uff1a\u8981\u641c\u7d22\u7684\u5b57\u6bb5\u540d\u79f0\u3002<\/li>\n<li><strong>pattern<\/strong>\uff1a\u641c\u7d22\u6a21\u5f0f\u3002<\/li>\n<\/ul>\n<h3 id=\"sql-like-\u64cd\u4f5c\u7b26\u5b9e\u4f8b\">SQL LIKE \u64cd\u4f5c\u7b26\u5b9e\u4f8b<\/h3>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u9009\u53d6 name \u4ee5\u5b57\u6bcd &#8220;G&#8221; <strong>\u5f00\u59cb<\/strong>\u7684\u6240\u6709\u5ba2\u6237\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT * FROM Websites\nWHERE name LIKE 'G%';\n<\/code><\/pre>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u9009\u53d6 name \u4ee5\u5b57\u6bcd &#8220;k&#8221; <strong>\u7ed3\u5c3e<\/strong>\u7684\u6240\u6709\u5ba2\u6237\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT * FROM Websites\nWHERE name LIKE '%k';\n<\/code><\/pre>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u9009\u53d6 name \u5305\u542b\u6a21\u5f0f <strong>&#8220;oo&#8221;<\/strong> \u7684\u6240\u6709\u5ba2\u6237\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT * FROM Websites\nWHERE name LIKE '%oo%';\n<\/code><\/pre>\n<p>\u901a\u8fc7\u4f7f\u7528 NOT \u5173\u952e\u5b57\uff0c\u60a8\u53ef\u4ee5\u9009\u53d6\u4e0d\u5339\u914d\u6a21\u5f0f\u7684\u8bb0\u5f55\u3002<\/p>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u9009\u53d6 name <strong>\u4e0d\u5305\u542b\u6a21\u5f0f &#8220;oo&#8221;<\/strong> \u7684\u6240\u6709\u5ba2\u6237\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT * FROM Websites\nWHERE name NOT LIKE '%oo%';\n<\/code><\/pre>\n<hr \/>\n<h2 id=\"sql-\u901a\u914d\u7b26\">SQL \u901a\u914d\u7b26<\/h2>\n<p>\u5728 SQL \u4e2d\uff0c\u901a\u914d\u7b26\u4e0e SQL LIKE \u64cd\u4f5c\u7b26\u4e00\u8d77\u4f7f\u7528\u3002<\/p>\n<p>SQL \u901a\u914d\u7b26\u7528\u4e8e\u641c\u7d22\u8868\u4e2d\u7684\u6570\u636e\u3002<\/p>\n<p>\u5728 SQL \u4e2d\uff0c\u53ef\u4f7f\u7528\u4ee5\u4e0b\u901a\u914d\u7b26\uff1a<\/p>\n<figure class=\"table-figure\">\n<table>\n<thead>\n<tr>\n<th style=\"text-align: left;\">\u901a\u914d\u7b26<\/th>\n<th style=\"text-align: left;\">\u63cf\u8ff0<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td style=\"text-align: left;\">%<\/td>\n<td style=\"text-align: left;\">\u66ff\u4ee3 0 \u4e2a\u6216\u591a\u4e2a\u5b57\u7b26<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">_<\/td>\n<td style=\"text-align: left;\">\u66ff\u4ee3\u4e00\u4e2a\u5b57\u7b26<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">[<em>charlist<\/em>]<\/td>\n<td style=\"text-align: left;\">\u5b57\u7b26\u5217\u4e2d\u7684\u4efb\u4f55\u5355\u4e00\u5b57\u7b26<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">[^<em>charlist<\/em>] \u6216 [!<em>charlist<\/em>]<\/td>\n<td style=\"text-align: left;\">\u4e0d\u5728\u5b57\u7b26\u5217\u4e2d\u7684\u4efb<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<h3 id=\"\u4f7f\u7528-sql--\u901a\u914d\u7b26\">\u4f7f\u7528 SQL % \u901a\u914d\u7b26<\/h3>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u9009\u53d6 url \u4ee5\u5b57\u6bcd &#8220;https&#8221; \u5f00\u59cb\u7684\u6240\u6709\u7f51\u7ad9\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT * FROM Websites\nWHERE url LIKE 'https%';\n<\/code><\/pre>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u9009\u53d6 url \u5305\u542b\u6a21\u5f0f &#8220;oo&#8221; \u7684\u6240\u6709\u7f51\u7ad9\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT * FROM Websites\nWHERE url LIKE '%oo%';\n<\/code><\/pre>\n<h3 id=\"\u4f7f\u7528-sql--\u901a\u914d\u7b26-2\">\u4f7f\u7528 SQL _ \u901a\u914d\u7b26<\/h3>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u9009\u53d6 name \u4ee5\u4e00\u4e2a\u4efb\u610f\u5b57\u7b26\u5f00\u59cb\uff0c\u7136\u540e\u662f &#8220;oogle&#8221; \u7684\u6240\u6709\u5ba2\u6237\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT * FROM Websites\nWHERE name LIKE '_oogle';\n<\/code><\/pre>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u9009\u53d6 name \u4ee5 &#8220;G&#8221; \u5f00\u59cb\uff0c\u7136\u540e\u662f\u4e00\u4e2a\u4efb\u610f\u5b57\u7b26\uff0c\u7136\u540e\u662f &#8220;o&#8221;\uff0c\u7136\u540e\u662f\u4e00\u4e2a\u4efb\u610f\u5b57\u7b26\uff0c\u7136\u540e\u662f &#8220;le&#8221; \u7684\u6240\u6709\u7f51\u7ad9\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT * FROM Websites\nWHERE name LIKE 'G_o_le';\n<\/code><\/pre>\n<h3 id=\"\u4f7f\u7528-sql-charlist-\u901a\u914d\u7b26\">\u4f7f\u7528 SQL [charlist] \u901a\u914d\u7b26<\/h3>\n<p>MySQL \u4e2d\u4f7f\u7528 <strong>REGEXP<\/strong> \u6216 <strong>NOT REGEXP<\/strong> \u8fd0\u7b97\u7b26 (\u6216 RLIKE \u548c NOT RLIKE) \u6765\u64cd\u4f5c\u6b63\u5219\u8868\u8fbe\u5f0f\u3002<\/p>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u9009\u53d6 name \u4ee5 &#8220;G&#8221;\u3001&#8221;F&#8221; \u6216 &#8220;s&#8221; \u5f00\u59cb\u7684\u6240\u6709\u7f51\u7ad9\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT * FROM Websites\nWHERE name REGEXP '^[GFs]';\n<\/code><\/pre>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u9009\u53d6 name \u4ee5 A \u5230 H \u5b57\u6bcd\u5f00\u5934\u7684\u7f51\u7ad9\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT * FROM Websites\nWHERE name REGEXP '^[A-H]';\n<\/code><\/pre>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u9009\u53d6 name \u4e0d\u4ee5 A \u5230 H \u5b57\u6bcd\u5f00\u5934\u7684\u7f51\u7ad9\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT * FROM Websites\nWHERE name REGEXP '^[^A-H]';\n<\/code><\/pre>\n<hr \/>\n<h2 id=\"in-\u64cd\u4f5c\u7b26\">IN \u64cd\u4f5c\u7b26<\/h2>\n<p>IN \u64cd\u4f5c\u7b26\u5141\u8bb8\u60a8\u5728 WHERE \u5b50\u53e5\u4e2d\u89c4\u5b9a\u591a\u4e2a\u503c\u3002<\/p>\n<h3 id=\"sql-in-\u8bed\u6cd5\">SQL IN \u8bed\u6cd5<\/h3>\n<pre><code>SELECT column1, column2, ...\nFROM table_name\nWHERE column IN (value1, value2, ...);\n<\/code><\/pre>\n<p>\u53c2\u6570\u8bf4\u660e\uff1a<\/p>\n<ul>\n<li><strong>column1, column2, &#8230;<\/strong>\uff1a\u8981\u9009\u62e9\u7684\u5b57\u6bb5\u540d\u79f0\uff0c\u53ef\u4ee5\u4e3a\u591a\u4e2a\u5b57\u6bb5\u3002\u5982\u679c\u4e0d\u6307\u5b9a\u5b57\u6bb5\u540d\u79f0\uff0c\u5219\u4f1a\u9009\u62e9\u6240\u6709\u5b57\u6bb5\u3002<\/li>\n<li><strong>table_name<\/strong>\uff1a\u8981\u67e5\u8be2\u7684\u8868\u540d\u79f0\u3002<\/li>\n<li><strong>column<\/strong>\uff1a\u8981\u67e5\u8be2\u7684\u5b57\u6bb5\u540d\u79f0\u3002<\/li>\n<li><strong>value1, value2, &#8230;<\/strong>\uff1a\u8981\u67e5\u8be2\u7684\u503c\uff0c\u53ef\u4ee5\u4e3a\u591a\u4e2a\u503c\u3002<\/li>\n<\/ul>\n<h3 id=\"in-\u64cd\u4f5c\u7b26\u5b9e\u4f8b\">IN \u64cd\u4f5c\u7b26\u5b9e\u4f8b<\/h3>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u9009\u53d6 name \u4e3a &#8220;Google&#8221; \u6216 &#8220;Vanforever&#8221; \u7684\u6240\u6709\u7f51\u7ad9\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT * FROM Websites\nWHERE name IN ('Google','Vanforever');\n<\/code><\/pre>\n<hr \/>\n<h2 id=\"sql-between-\u64cd\u4f5c\u7b26\">SQL BETWEEN \u64cd\u4f5c\u7b26<\/h2>\n<p>BETWEEN \u64cd\u4f5c\u7b26\u9009\u53d6\u4ecb\u4e8e\u4e24\u4e2a\u503c\u4e4b\u95f4\u7684\u6570\u636e\u8303\u56f4\u5185\u7684\u503c\u3002\u8fd9\u4e9b\u503c\u53ef\u4ee5\u662f\u6570\u503c\u3001\u6587\u672c\u6216\u8005\u65e5\u671f\u3002<\/p>\n<h3 id=\"sql-between-\u8bed\u6cd5\">SQL BETWEEN \u8bed\u6cd5<\/h3>\n<pre><code>SELECT column1, column2, ...\nFROM table_name\nWHERE column BETWEEN value1 AND value2;\n<\/code><\/pre>\n<p>\u53c2\u6570\u8bf4\u660e\uff1a<\/p>\n<ul>\n<li>column1, column2, &#8230;\uff1a\u8981\u9009\u62e9\u7684\u5b57\u6bb5\u540d\u79f0\uff0c\u53ef\u4ee5\u4e3a\u591a\u4e2a\u5b57\u6bb5\u3002\u5982\u679c\u4e0d\u6307\u5b9a\u5b57\u6bb5\u540d\u79f0\uff0c\u5219\u4f1a\u9009\u62e9\u6240\u6709\u5b57\u6bb5\u3002<\/li>\n<li>table_name\uff1a\u8981\u67e5\u8be2\u7684\u8868\u540d\u79f0\u3002<\/li>\n<li>column\uff1a\u8981\u67e5\u8be2\u7684\u5b57\u6bb5\u540d\u79f0\u3002<\/li>\n<li>value1\uff1a\u8303\u56f4\u7684\u8d77\u59cb\u503c\u3002<\/li>\n<li>value2\uff1a\u8303\u56f4\u7684\u7ed3\u675f\u503c\u3002<\/li>\n<\/ul>\n<h3 id=\"between-\u64cd\u4f5c\u7b26\u5b9e\u4f8b\">BETWEEN \u64cd\u4f5c\u7b26\u5b9e\u4f8b<\/h3>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u9009\u53d6 alexa \u4ecb\u4e8e 1 \u548c 20 \u4e4b\u95f4\u7684\u6240\u6709\u7f51\u7ad9\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT * FROM Websites\nWHERE alexa BETWEEN 1 AND 20;\n<\/code><\/pre>\n<h3 id=\"not-between-\u64cd\u4f5c\u7b26\u5b9e\u4f8b\">NOT BETWEEN \u64cd\u4f5c\u7b26\u5b9e\u4f8b<\/h3>\n<p>\u5982\u9700\u663e\u793a\u4e0d\u5728\u4e0a\u9762\u5b9e\u4f8b\u8303\u56f4\u5185\u7684\u7f51\u7ad9\uff0c\u8bf7\u4f7f\u7528 NOT BETWEEN\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT * FROM Websites\nWHERE alexa NOT BETWEEN 1 AND 20;\n<\/code><\/pre>\n<h3 id=\"\u5e26\u6709-in-\u7684-between-\u64cd\u4f5c\u7b26\u5b9e\u4f8b\">\u5e26\u6709 IN \u7684 BETWEEN \u64cd\u4f5c\u7b26\u5b9e\u4f8b<\/h3>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u9009\u53d6 alexa \u4ecb\u4e8e 1 \u548c 20 \u4e4b\u95f4\u4f46 country \u4e0d\u4e3a USA \u548c IND \u7684\u6240\u6709\u7f51\u7ad9\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT * FROM Websites\nWHERE (alexa BETWEEN 1 AND 20)\nAND country NOT IN ('USA', 'IND');\n<\/code><\/pre>\n<h3 id=\"\u5e26\u6709\u6587\u672c\u503c\u7684-between-\u64cd\u4f5c\u7b26\u5b9e\u4f8b\">\u5e26\u6709\u6587\u672c\u503c\u7684 BETWEEN \u64cd\u4f5c\u7b26\u5b9e\u4f8b<\/h3>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u9009\u53d6 name \u4ee5\u4ecb\u4e8e &#8216;A&#8217; \u548c &#8216;H&#8217; \u4e4b\u95f4\u5b57\u6bcd\u5f00\u59cb\u7684\u6240\u6709\u7f51\u7ad9\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT * FROM Websites\nWHERE name BETWEEN 'A' AND 'H';\n<\/code><\/pre>\n<h3 id=\"\u5e26\u6709\u6587\u672c\u503c\u7684-not-between-\u64cd\u4f5c\u7b26\u5b9e\u4f8b\">\u5e26\u6709\u6587\u672c\u503c\u7684 NOT BETWEEN \u64cd\u4f5c\u7b26\u5b9e\u4f8b<\/h3>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u9009\u53d6 name \u4e0d\u4ecb\u4e8e &#8216;A&#8217; \u548c &#8216;H&#8217; \u4e4b\u95f4\u5b57\u6bcd\u5f00\u59cb\u7684\u6240\u6709\u7f51\u7ad9\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT * FROM Websites\nWHERE name NOT BETWEEN 'A' AND 'H';\n<\/code><\/pre>\n<h3 id=\"\u5e26\u6709\u65e5\u671f\u503c\u7684-between-\u64cd\u4f5c\u7b26\u5b9e\u4f8b\">\u5e26\u6709\u65e5\u671f\u503c\u7684 BETWEEN \u64cd\u4f5c\u7b26\u5b9e\u4f8b<\/h3>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u9009\u53d6 date \u4ecb\u4e8e &#8216;2016-05-10&#8217; \u548c &#8216;2016-05-14&#8217; \u4e4b\u95f4\u7684\u6240\u6709\u8bbf\u95ee\u8bb0\u5f55\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT * FROM access_log\nWHERE date BETWEEN '2016-05-10' AND '2016-05-14';\n<\/code><\/pre>\n<hr \/>\n<h2 id=\"sql-\u522b\u540d\">SQL \u522b\u540d<\/h2>\n<p>\u901a\u8fc7\u4f7f\u7528 SQL\uff0c\u53ef\u4ee5\u4e3a\u8868\u540d\u79f0\u6216\u5217\u540d\u79f0\u6307\u5b9a\u522b\u540d\u3002<\/p>\n<p>\u57fa\u672c\u4e0a\uff0c\u521b\u5efa\u522b\u540d\u662f\u4e3a\u4e86\u8ba9\u5217\u540d\u79f0\u7684\u53ef\u8bfb\u6027\u66f4\u5f3a\u3002<\/p>\n<h3 id=\"\u5217\u7684-sql-\u522b\u540d\u8bed\u6cd5\">\u5217\u7684 SQL \u522b\u540d\u8bed\u6cd5<\/h3>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT column_name AS alias_name\nFROM table_name;\n<\/code><\/pre>\n<h3 id=\"\u8868\u7684-sql-\u522b\u540d\u8bed\u6cd5\">\u8868\u7684 SQL \u522b\u540d\u8bed\u6cd5<\/h3>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT column_name(s)\nFROM table_name AS alias_name;\n<\/code><\/pre>\n<h3 id=\"\u5217\u7684\u522b\u540d\u5b9e\u4f8b\">\u5217\u7684\u522b\u540d\u5b9e\u4f8b<\/h3>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u6307\u5b9a\u4e86\u4e24\u4e2a\u522b\u540d\uff0c\u4e00\u4e2a\u662f name \u5217\u7684\u522b\u540d\uff0c\u4e00\u4e2a\u662f country \u5217\u7684\u522b\u540d\u3002<strong>\u63d0\u793a\uff1a<\/strong>\u5982\u679c\u5217\u540d\u79f0\u5305\u542b\u7a7a\u683c\uff0c\u8981\u6c42\u4f7f\u7528\u53cc\u5f15\u53f7\u6216\u65b9\u62ec\u53f7\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT name AS n, country AS c\nFROM Websites;\n<\/code><\/pre>\n<p>\u5728\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u4e2d\uff0c\u6211\u4eec\u628a\u4e09\u4e2a\u5217\uff08url\u3001alexa \u548c country\uff09\u7ed3\u5408\u5728\u4e00\u8d77\uff0c\u5e76\u521b\u5efa\u4e00\u4e2a\u540d\u4e3a &#8220;site_info&#8221; \u7684\u522b\u540d\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT name, CONCAT(url, ', ', alexa, ', ', country) AS site_info\nFROM Websites;\n<\/code><\/pre>\n<h3 id=\"\u8868\u7684\u522b\u540d\u5b9e\u4f8b\">\u8868\u7684\u522b\u540d\u5b9e\u4f8b<\/h3>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u9009\u53d6 &#8220;Baidu&#8221; \u7684\u6240\u6709\u8bbf\u95ee\u8bb0\u5f55\u3002\u6211\u4eec\u4f7f\u7528 &#8220;Websites&#8221; \u548c &#8220;access_log&#8221; \u8868\uff0c\u5e76\u5206\u522b\u4e3a\u5b83\u4eec\u6307\u5b9a\u8868\u522b\u540d &#8220;w&#8221; \u548c &#8220;a&#8221;\uff08\u901a\u8fc7\u4f7f\u7528\u522b\u540d\u8ba9 SQL \u66f4\u7b80\u77ed\uff09\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT w.name, w.url, a.count, a.date\nFROM Websites AS w, access_log AS a\nWHERE a.site_id=w.id and w.name=\"Baidu\";\n<\/code><\/pre>\n<p>\u4e0d\u5e26\u522b\u540d\u7684\u76f8\u540c\u7684 SQL \u8bed\u53e5\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT Websites.name, Websites.url, access_log.count, access_log.date\nFROM Websites, access_log\nWHERE Websites.id=access_log.site_id and Websites.name=\"Baidu\";\n<\/code><\/pre>\n<p>\u5728\u4e0b\u9762\u7684\u60c5\u51b5\u4e0b\uff0c\u4f7f\u7528\u522b\u540d\u5f88\u6709\u7528\uff1a<\/p>\n<ul>\n<li>\u5728\u67e5\u8be2\u4e2d\u6d89\u53ca\u8d85\u8fc7\u4e00\u4e2a\u8868<\/li>\n<li>\u5728\u67e5\u8be2\u4e2d\u4f7f\u7528\u4e86\u51fd\u6570<\/li>\n<li>\u5217\u540d\u79f0\u5f88\u957f\u6216\u8005\u53ef\u8bfb\u6027\u5dee<\/li>\n<li>\u9700\u8981\u628a\u4e24\u4e2a\u5217\u6216\u8005\u591a\u4e2a\u5217\u7ed3\u5408\u5728\u4e00\u8d77<\/li>\n<\/ul>\n<hr \/>\n<h2 id=\"sql-join\">SQL JOIN<\/h2>\n<p>SQL JOIN \u5b50\u53e5\u7528\u4e8e\u628a\u6765\u81ea\u4e24\u4e2a\u6216\u591a\u4e2a\u8868\u7684\u884c\u7ed3\u5408\u8d77\u6765\uff0c\u57fa\u4e8e\u8fd9\u4e9b\u8868\u4e4b\u95f4\u7684\u5171\u540c\u5b57\u6bb5\u3002<\/p>\n<p>\u4e0b\u56fe\u5c55\u793a\u4e86 LEFT JOIN\u3001RIGHT JOIN\u3001INNER JOIN\u3001OUTER JOIN \u76f8\u5173\u7684 7 \u79cd\u7528\u6cd5\u3002<\/p>\n<p><div class='fancybox-wrapper lazyload-container-unload' data-fancybox='post-images' href='https:\/\/pic.vanforever.com.cn\/MySQL\/20240423\/2024042301.jpg'><img class=\"lazyload lazyload-style-1\" src=\"data:image\/svg+xml;base64,PCEtLUFyZ29uTG9hZGluZy0tPgo8c3ZnIHdpZHRoPSIxIiBoZWlnaHQ9IjEiIHhtbG5zPSJodHRwOi8vd3d3LnczLm9yZy8yMDAwL3N2ZyIgc3Ryb2tlPSIjZmZmZmZmMDAiPjxnPjwvZz4KPC9zdmc+\"  decoding=\"async\" data-original=\"https:\/\/pic.vanforever.com.cn\/MySQL\/20240423\/2024042301.jpg\" src=\"data:image\/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsQAAA7EAZUrDhsAAAANSURBVBhXYzh8+PB\/AAffA0nNPuCLAAAAAElFTkSuQmCC\" \/><\/div><\/p>\n<p>\u6700\u5e38\u89c1\u7684 JOIN \u7c7b\u578b\uff1a<strong>SQL INNER JOIN\uff08\u7b80\u5355\u7684 JOIN\uff09<\/strong>\u3002 SQL INNER JOIN \u4ece\u591a\u4e2a\u8868\u4e2d\u8fd4\u56de\u6ee1\u8db3 JOIN \u6761\u4ef6\u7684\u6240\u6709\u884c\u3002<\/p>\n<h3 id=\"\u8bed\u6cd5\">\u8bed\u6cd5\uff1a<\/h3>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT column1, column2, ...\nFROM table1\nJOIN table2 ON condition;\n<\/code><\/pre>\n<p><strong>\u53c2\u6570\u8bf4\u660e\uff1a<\/strong><\/p>\n<ul>\n<li><strong>column1, column2, &#8230;<\/strong>\uff1a\u8981\u9009\u62e9\u7684\u5b57\u6bb5\u540d\u79f0\uff0c\u53ef\u4ee5\u4e3a\u591a\u4e2a\u5b57\u6bb5\u3002\u5982\u679c\u4e0d\u6307\u5b9a\u5b57\u6bb5\u540d\u79f0\uff0c\u5219\u4f1a\u9009\u62e9\u6240\u6709\u5b57\u6bb5\u3002<\/li>\n<li><strong>table1<\/strong>\uff1a\u8981\u8fde\u63a5\u7684\u7b2c\u4e00\u4e2a\u8868\u3002<\/li>\n<li><strong>table2<\/strong>\uff1a\u8981\u8fde\u63a5\u7684\u7b2c\u4e8c\u4e2a\u8868\u3002<\/li>\n<li><strong>condition<\/strong>\uff1a\u8fde\u63a5\u6761\u4ef6\uff0c\u7528\u4e8e\u6307\u5b9a\u8fde\u63a5\u65b9\u5f0f\u3002<\/li>\n<\/ul>\n<p>\u4e0b\u9762\u662f\u9009\u81ea &#8220;Websites&#8221; \u8868\u7684\u6570\u636e\uff1a<\/p>\n<figure class=\"table-figure\">\n<table>\n<thead>\n<tr>\n<th>id<\/th>\n<th>name<\/th>\n<th>url<\/th>\n<th>alexa<\/th>\n<th>country<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>1<\/td>\n<td>Google<\/td>\n<td><a class=\"url\" href=\"https:\/\/www.google.cm\/\" target=\"_blank\" rel=\"noopener\">https:\/\/www.google.cm\/<\/a><\/td>\n<td>1<\/td>\n<td>USA<\/td>\n<\/tr>\n<tr>\n<td>2<\/td>\n<td>\u6dd8\u5b9d<\/td>\n<td><a class=\"url\" href=\"https:\/\/www.taobao.com\/\" target=\"_blank\" rel=\"noopener\">https:\/\/www.taobao.com\/<\/a><\/td>\n<td>13<\/td>\n<td>CN<\/td>\n<\/tr>\n<tr>\n<td>3<\/td>\n<td>vanforever<\/td>\n<td><a class=\"url\" href=\"https:\/\/www.vanforever.com.cn\/\" target=\"_blank\" rel=\"noopener\">https:\/\/www.vanforever.com.cn\/<\/a><\/td>\n<td>4689<\/td>\n<td>CN<\/td>\n<\/tr>\n<tr>\n<td>4<\/td>\n<td>\u5fae\u535a<\/td>\n<td><a class=\"url\" href=\"http:\/\/weibo.com\/\" target=\"_blank\" rel=\"noopener\">http:\/\/weibo.com\/<\/a><\/td>\n<td>20<\/td>\n<td>CN<\/td>\n<\/tr>\n<tr>\n<td>5<\/td>\n<td>Facebook<\/td>\n<td><a class=\"url\" href=\"https:\/\/www.facebook.com\/\" target=\"_blank\" rel=\"noopener\">https:\/\/www.facebook.com\/<\/a><\/td>\n<td>3<\/td>\n<td>USA<\/td>\n<\/tr>\n<tr>\n<td>6<\/td>\n<td>stackoverflow<\/td>\n<td><a class=\"url\" href=\"http:\/\/stackoverflow.com\/\" target=\"_blank\" rel=\"noopener\">http:\/\/stackoverflow.com\/<\/a><\/td>\n<td>0<\/td>\n<td>IND<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<p>\u4e0b\u9762\u662f &#8220;access_log&#8221; \u7f51\u7ad9\u8bbf\u95ee\u8bb0\u5f55\u8868\u7684\u6570\u636e\uff1a<\/p>\n<figure class=\"table-figure\">\n<table>\n<thead>\n<tr>\n<th>aid<\/th>\n<th>site_id<\/th>\n<th>count<\/th>\n<th>date<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>1<\/td>\n<td>1<\/td>\n<td>45<\/td>\n<td>2024-05-10<\/td>\n<\/tr>\n<tr>\n<td>2<\/td>\n<td>3<\/td>\n<td>100<\/td>\n<td>2024-05-13<\/td>\n<\/tr>\n<tr>\n<td>3<\/td>\n<td>1<\/td>\n<td>230<\/td>\n<td>2024-05-14<\/td>\n<\/tr>\n<tr>\n<td>4<\/td>\n<td>2<\/td>\n<td>10<\/td>\n<td>2024-05-14<\/td>\n<\/tr>\n<tr>\n<td>5<\/td>\n<td>5<\/td>\n<td>205<\/td>\n<td>2024-05-14<\/td>\n<\/tr>\n<tr>\n<td>6<\/td>\n<td>4<\/td>\n<td>13<\/td>\n<td>2024-05-15<\/td>\n<\/tr>\n<tr>\n<td>7<\/td>\n<td>3<\/td>\n<td>220<\/td>\n<td>2024-05-15<\/td>\n<\/tr>\n<tr>\n<td>8<\/td>\n<td>5<\/td>\n<td>545<\/td>\n<td>2024-05-16<\/td>\n<\/tr>\n<tr>\n<td>9<\/td>\n<td>3<\/td>\n<td>201<\/td>\n<td>2024-05-17<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<p>\u8bf7\u6ce8\u610f\uff0c&#8221;Websites&#8221; \u8868\u4e2d\u7684 &#8220;<strong>id<\/strong>&#8221; \u5217\u6307\u5411 &#8220;access_log&#8221; \u8868\u4e2d\u7684\u5b57\u6bb5 &#8220;<strong>site_id<\/strong>&#8220;\u3002\u4e0a\u9762\u8fd9\u4e24\u4e2a\u8868\u662f\u901a\u8fc7 &#8220;site_id&#8221; \u5217\u8054\u7cfb\u8d77\u6765\u7684\u3002<\/p>\n<p>\u7136\u540e\uff0c\u5982\u679c\u6211\u4eec\u8fd0\u884c\u4e0b\u9762\u7684 SQL \u8bed\u53e5\uff08\u5305\u542b INNER JOIN\uff09\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT Websites.id, Websites.name, access_log.count, access_log.date\nFROM Websites\nINNER JOIN access_log\nON Websites.id=access_log.site_id;\n<\/code><\/pre>\n<p>\u6267\u884c\u4ee5\u4e0a SQL \u8f93\u51fa\u7ed3\u679c\u5982\u4e0b\uff1a<\/p>\n<p><div class='fancybox-wrapper lazyload-container-unload' data-fancybox='post-images' href='https:\/\/pic.vanforever.com.cn\/MySQL\/20240423\/2024042302.jpg'><img class=\"lazyload lazyload-style-1\" src=\"data:image\/svg+xml;base64,PCEtLUFyZ29uTG9hZGluZy0tPgo8c3ZnIHdpZHRoPSIxIiBoZWlnaHQ9IjEiIHhtbG5zPSJodHRwOi8vd3d3LnczLm9yZy8yMDAwL3N2ZyIgc3Ryb2tlPSIjZmZmZmZmMDAiPjxnPjwvZz4KPC9zdmc+\"  decoding=\"async\" data-original=\"https:\/\/pic.vanforever.com.cn\/MySQL\/20240423\/2024042302.jpg\" src=\"data:image\/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsQAAA7EAZUrDhsAAAANSURBVBhXYzh8+PB\/AAffA0nNPuCLAAAAAElFTkSuQmCC\" \/><\/div><\/p>\n<hr \/>\n<h2 id=\"sql-inner-join-\u5173\u952e\u5b57\">SQL INNER JOIN \u5173\u952e\u5b57<\/h2>\n<p>INNER JOIN \u5173\u952e\u5b57\u5728\u8868\u4e2d\u5b58\u5728\u81f3\u5c11\u4e00\u4e2a\u5339\u914d\u65f6\u8fd4\u56de\u884c\u3002<\/p>\n<h3 id=\"sql-inner-join-\u8bed\u6cd5\">SQL INNER JOIN \u8bed\u6cd5<\/h3>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT *column_name(s)*\nFROM *table1*\nINNER JOIN *table2*\nON *table1.column_name*=*table2.column_name*;\n<\/code><\/pre>\n<p>\u6216\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT *column_name(s)*\nFROM *table1*\nJOIN *table2*\nON *table1.column_name*=*table2.column_name*;\n<\/code><\/pre>\n<p><strong>\u53c2\u6570\u8bf4\u660e\uff1a<\/strong><\/p>\n<ul>\n<li>columns\uff1a\u8981\u663e\u793a\u7684\u5217\u540d\u3002<\/li>\n<li>table1\uff1a\u88681\u7684\u540d\u79f0\u3002<\/li>\n<li>table2\uff1a\u88682\u7684\u540d\u79f0\u3002<\/li>\n<li>column_name\uff1a\u8868\u4e2d\u7528\u4e8e\u8fde\u63a5\u7684\u5217\u540d\u3002<\/li>\n<\/ul>\n<p><strong>\u6ce8\u91ca\uff1a<\/strong>INNER JOIN \u4e0e JOIN \u662f\u76f8\u540c\u7684\u3002<\/p>\n<h3 id=\"sql-inner-join-\u5b9e\u4f8b\">SQL INNER JOIN \u5b9e\u4f8b<\/h3>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u5c06\u8fd4\u56de\u6240\u6709\u7f51\u7ad9\u7684\u8bbf\u95ee\u8bb0\u5f55\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT Websites.name, access_log.count, access_log.date\nFROM Websites\nINNER JOIN access_log\nON Websites.id=access_log.site_id\nORDER BY access_log.count;\n<\/code><\/pre>\n<p><div class='fancybox-wrapper lazyload-container-unload' data-fancybox='post-images' href='https:\/\/pic.vanforever.com.cn\/MySQL\/20240424\/2024042401.jpg'><img class=\"lazyload lazyload-style-1\" src=\"data:image\/svg+xml;base64,PCEtLUFyZ29uTG9hZGluZy0tPgo8c3ZnIHdpZHRoPSIxIiBoZWlnaHQ9IjEiIHhtbG5zPSJodHRwOi8vd3d3LnczLm9yZy8yMDAwL3N2ZyIgc3Ryb2tlPSIjZmZmZmZmMDAiPjxnPjwvZz4KPC9zdmc+\"  decoding=\"async\" data-original=\"https:\/\/pic.vanforever.com.cn\/MySQL\/20240424\/2024042401.jpg\" src=\"data:image\/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsQAAA7EAZUrDhsAAAANSURBVBhXYzh8+PB\/AAffA0nNPuCLAAAAAElFTkSuQmCC\" \/><\/div><\/p>\n<hr \/>\n<h2 id=\"sql-left-join-\u5173\u952e\u5b57\">SQL LEFT JOIN \u5173\u952e\u5b57<\/h2>\n<p>LEFT JOIN \u5173\u952e\u5b57\u4ece\u5de6\u8868\uff08table1\uff09\u8fd4\u56de\u6240\u6709\u7684\u884c\uff0c\u5373\u4f7f\u53f3\u8868\uff08table2\uff09\u4e2d\u6ca1\u6709\u5339\u914d\u3002\u5982\u679c\u53f3\u8868\u4e2d\u6ca1\u6709\u5339\u914d\uff0c\u5219\u7ed3\u679c\u4e3a NULL\u3002<\/p>\n<h3 id=\"sql-left-join-\u8bed\u6cd5\">SQL LEFT JOIN \u8bed\u6cd5<\/h3>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT *column_name(s)*\nFROM *table1*\nLEFT JOIN *table2*\nON *table1.column_name*=*table2.column_name*;\n<\/code><\/pre>\n<p>\u6216\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT *column_name(s)*\nFROM *table1*\nLEFT OUTER JOIN *table2*\nON *table1.column_name*=*table2.column_name*;\n<\/code><\/pre>\n<h3 id=\"sql-left-join-\u5b9e\u4f8b\">SQL LEFT JOIN \u5b9e\u4f8b<\/h3>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u5c06\u8fd4\u56de\u6240\u6709\u7f51\u7ad9\u53ca\u4ed6\u4eec\u7684\u8bbf\u95ee\u91cf\uff08\u5982\u679c\u6709\u7684\u8bdd\uff09\u3002<\/p>\n<p>\u4ee5\u4e0b\u5b9e\u4f8b\u4e2d\u6211\u4eec\u628a Websites \u4f5c\u4e3a\u5de6\u8868\uff0caccess_log \u4f5c\u4e3a\u53f3\u8868\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT Websites.name, access_log.count, access_log.date\nFROM Websites\nLEFT JOIN access_log\nON Websites.id=access_log.site_id\nORDER BY access_log.count DESC;\n<\/code><\/pre>\n<p><div class='fancybox-wrapper lazyload-container-unload' data-fancybox='post-images' href='https:\/\/pic.vanforever.com.cn\/MySQL\/20240424\/2024042402.jpg'><img class=\"lazyload lazyload-style-1\" src=\"data:image\/svg+xml;base64,PCEtLUFyZ29uTG9hZGluZy0tPgo8c3ZnIHdpZHRoPSIxIiBoZWlnaHQ9IjEiIHhtbG5zPSJodHRwOi8vd3d3LnczLm9yZy8yMDAwL3N2ZyIgc3Ryb2tlPSIjZmZmZmZmMDAiPjxnPjwvZz4KPC9zdmc+\"  decoding=\"async\" data-original=\"https:\/\/pic.vanforever.com.cn\/MySQL\/20240424\/2024042402.jpg\" src=\"data:image\/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsQAAA7EAZUrDhsAAAANSURBVBhXYzh8+PB\/AAffA0nNPuCLAAAAAElFTkSuQmCC\" \/><\/div><\/p>\n<hr \/>\n<h2 id=\"sql-right-join-\u5173\u952e\u5b57\">SQL RIGHT JOIN \u5173\u952e\u5b57<\/h2>\n<p>RIGHT JOIN \u5173\u952e\u5b57\u4ece\u53f3\u8868\uff08table2\uff09\u8fd4\u56de\u6240\u6709\u7684\u884c\uff0c\u5373\u4f7f\u5de6\u8868\uff08table1\uff09\u4e2d\u6ca1\u6709\u5339\u914d\u3002\u5982\u679c\u5de6\u8868\u4e2d\u6ca1\u6709\u5339\u914d\uff0c\u5219\u7ed3\u679c\u4e3a NULL\u3002<\/p>\n<h3 id=\"sql-right-join-\u8bed\u6cd5\">SQL RIGHT JOIN \u8bed\u6cd5<\/h3>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT *column_name(s)*\nFROM *table1*\nRIGHT JOIN *table2*\nON *table1.column_name*=*table2.column_name*;\n<\/code><\/pre>\n<p>\u6216\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT *column_name(s)*\nFROM *table1*\nRIGHT OUTER JOIN *table2*\nON *table1.column_name*=*table2.column_name*;\n<\/code><\/pre>\n<h3 id=\"sql-right-join-\u5b9e\u4f8b\">SQL RIGHT JOIN \u5b9e\u4f8b<\/h3>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u5c06\u8fd4\u56de\u7f51\u7ad9\u7684\u8bbf\u95ee\u8bb0\u5f55\u3002<\/p>\n<p>\u4ee5\u4e0b\u5b9e\u4f8b\u4e2d\u6211\u4eec\u628a Websites \u4f5c\u4e3a\u5de6\u8868\uff0caccess_log \u4f5c\u4e3a\u53f3\u8868\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT websites.name, access_log.count, access_log.date\nFROM websites\nRIGHT JOIN access_log\nON access_log.site_id=websites.id\nORDER BY access_log.count DESC;\n<\/code><\/pre>\n<p><div class='fancybox-wrapper lazyload-container-unload' data-fancybox='post-images' href='https:\/\/pic.vanforever.com.cn\/MySQL\/20240424\/2024042403.jpg'><img class=\"lazyload lazyload-style-1\" src=\"data:image\/svg+xml;base64,PCEtLUFyZ29uTG9hZGluZy0tPgo8c3ZnIHdpZHRoPSIxIiBoZWlnaHQ9IjEiIHhtbG5zPSJodHRwOi8vd3d3LnczLm9yZy8yMDAwL3N2ZyIgc3Ryb2tlPSIjZmZmZmZmMDAiPjxnPjwvZz4KPC9zdmc+\"  decoding=\"async\" data-original=\"https:\/\/pic.vanforever.com.cn\/MySQL\/20240424\/2024042403.jpg\" src=\"data:image\/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsQAAA7EAZUrDhsAAAANSURBVBhXYzh8+PB\/AAffA0nNPuCLAAAAAElFTkSuQmCC\" \/><\/div><\/p>\n<hr \/>\n<h2 id=\"sql-union-\u64cd\u4f5c\u7b26\">SQL UNION \u64cd\u4f5c\u7b26<\/h2>\n<p>UNION \u64cd\u4f5c\u7b26\u7528\u4e8e\u5408\u5e76\u4e24\u4e2a\u6216\u591a\u4e2a SELECT \u8bed\u53e5\u7684\u7ed3\u679c\u96c6\u3002<\/p>\n<p>\u8bf7\u6ce8\u610f\uff0cUNION \u5185\u90e8\u7684\u6bcf\u4e2a SELECT \u8bed\u53e5\u5fc5\u987b\u62e5\u6709\u76f8\u540c\u6570\u91cf\u7684\u5217\u3002\u5217\u4e5f\u5fc5\u987b\u62e5\u6709\u76f8\u4f3c\u7684\u6570\u636e\u7c7b\u578b\u3002\u540c\u65f6\uff0c\u6bcf\u4e2a SELECT \u8bed\u53e5\u4e2d\u7684\u5217\u7684\u987a\u5e8f\u5fc5\u987b\u76f8\u540c\u3002<\/p>\n<h3 id=\"sql-union-\u8bed\u6cd5\">SQL UNION \u8bed\u6cd5<\/h3>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT *column_name(s)* FROM *table1*\nUNION\nSELECT *column_name(s)* FROM *table2*;\n<\/code><\/pre>\n<p><strong>\u6ce8\u91ca\uff1a<\/strong>\u9ed8\u8ba4\u5730\uff0cUNION \u64cd\u4f5c\u7b26\u9009\u53d6\u4e0d\u540c\u7684\u503c\u3002\u5982\u679c\u5141\u8bb8\u91cd\u590d\u7684\u503c\uff0c\u8bf7\u4f7f\u7528 UNION ALL\u3002<\/p>\n<h3 id=\"sql-union-all-\u8bed\u6cd5\">SQL UNION ALL \u8bed\u6cd5<\/h3>\n<p>SELECT <em>column_name(s)<\/em> FROM <em>table1<\/em><br \/>\nUNION ALL<br \/>\nSELECT <em>column_name(s)<\/em> FROM <em>table2<\/em>;<\/p>\n<p><strong>\u6ce8\u91ca\uff1a<\/strong>UNION \u7ed3\u679c\u96c6\u4e2d\u7684\u5217\u540d\u603b\u662f\u7b49\u4e8e UNION \u4e2d\u7b2c\u4e00\u4e2a SELECT \u8bed\u53e5\u4e2d\u7684\u5217\u540d\u3002<\/p>\n<p>\u4e0b\u9762\u662f\u9009\u81ea &#8220;Websites&#8221; \u8868\u7684\u6570\u636e\uff1a<\/p>\n<figure class=\"table-figure\">\n<table>\n<thead>\n<tr>\n<th>id<\/th>\n<th>name<\/th>\n<th>url<\/th>\n<th>alexa<\/th>\n<th>country<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>1<\/td>\n<td>Google<\/td>\n<td><a class=\"url\" href=\"https:\/\/www.google.cm\/\" target=\"_blank\" rel=\"noopener\">https:\/\/www.google.cm\/<\/a><\/td>\n<td>1<\/td>\n<td>USA<\/td>\n<\/tr>\n<tr>\n<td>2<\/td>\n<td>\u6dd8\u5b9d<\/td>\n<td><a class=\"url\" href=\"https:\/\/www.taobao.com\/\" target=\"_blank\" rel=\"noopener\">https:\/\/www.taobao.com\/<\/a><\/td>\n<td>13<\/td>\n<td>CN<\/td>\n<\/tr>\n<tr>\n<td>3<\/td>\n<td>vanforever<\/td>\n<td><a class=\"url\" href=\"https:\/\/www.vanforever.com.cn\/\" target=\"_blank\" rel=\"noopener\">https:\/\/www.vanforever.com.cn\/<\/a><\/td>\n<td>4689<\/td>\n<td>CN<\/td>\n<\/tr>\n<tr>\n<td>4<\/td>\n<td>\u5fae\u535a<\/td>\n<td><a class=\"url\" href=\"http:\/\/weibo.com\/\" target=\"_blank\" rel=\"noopener\">http:\/\/weibo.com\/<\/a><\/td>\n<td>20<\/td>\n<td>CN<\/td>\n<\/tr>\n<tr>\n<td>5<\/td>\n<td>Facebook<\/td>\n<td><a class=\"url\" href=\"https:\/\/www.facebook.com\/\" target=\"_blank\" rel=\"noopener\">https:\/\/www.facebook.com\/<\/a><\/td>\n<td>3<\/td>\n<td>USA<\/td>\n<\/tr>\n<tr>\n<td>6<\/td>\n<td>stackoverflow<\/td>\n<td><a class=\"url\" href=\"http:\/\/stackoverflow.com\/\" target=\"_blank\" rel=\"noopener\">http:\/\/stackoverflow.com\/<\/a><\/td>\n<td>0<\/td>\n<td>IND<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<p>\u4e0b\u9762\u662f &#8220;apps&#8221; APP \u7684\u6570\u636e\uff1a<\/p>\n<figure class=\"table-figure\">\n<table>\n<thead>\n<tr>\n<th>id<\/th>\n<th>app_name<\/th>\n<th>url<\/th>\n<th>country<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>1<\/td>\n<td>QQ APP<\/td>\n<td><a class=\"url\" href=\"http:\/\/im.qq.com\/\" target=\"_blank\" rel=\"noopener\">http:\/\/im.qq.com\/<\/a><\/td>\n<td>CN<\/td>\n<\/tr>\n<tr>\n<td>2<\/td>\n<td>\u5fae\u535a APP<\/td>\n<td><a class=\"url\" href=\"http:\/\/weibo.com\/\" target=\"_blank\" rel=\"noopener\">http:\/\/weibo.com\/<\/a><\/td>\n<td>CN<\/td>\n<\/tr>\n<tr>\n<td>3<\/td>\n<td>\u6dd8\u5b9d APP<\/td>\n<td><a class=\"url\" href=\"https:\/\/www.taobao.com\/\" target=\"_blank\" rel=\"noopener\">https:\/\/www.taobao.com\/<\/a><\/td>\n<td>CN<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<h3 id=\"sql-union-\u5b9e\u4f8b\">SQL UNION \u5b9e\u4f8b<\/h3>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u4ece &#8220;Websites&#8221; \u548c &#8220;apps&#8221; \u8868\u4e2d\u9009\u53d6\u6240\u6709<strong>\u4e0d\u540c\u7684<\/strong>country\uff08\u53ea\u6709\u4e0d\u540c\u7684\u503c\uff09\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT country FROM Websites\nUNION\nSELECT country FROM apps\nORDER BY country;\n<\/code><\/pre>\n<p><div class='fancybox-wrapper lazyload-container-unload' data-fancybox='post-images' href='https:\/\/pic.vanforever.com.cn\/MySQL\/20240424\/2024042404.jpg'><img class=\"lazyload lazyload-style-1\" src=\"data:image\/svg+xml;base64,PCEtLUFyZ29uTG9hZGluZy0tPgo8c3ZnIHdpZHRoPSIxIiBoZWlnaHQ9IjEiIHhtbG5zPSJodHRwOi8vd3d3LnczLm9yZy8yMDAwL3N2ZyIgc3Ryb2tlPSIjZmZmZmZmMDAiPjxnPjwvZz4KPC9zdmc+\"  decoding=\"async\" data-original=\"https:\/\/pic.vanforever.com.cn\/MySQL\/20240424\/2024042404.jpg\" src=\"data:image\/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsQAAA7EAZUrDhsAAAANSURBVBhXYzh8+PB\/AAffA0nNPuCLAAAAAElFTkSuQmCC\" \/><\/div><\/p>\n<p><strong>\u6ce8\u91ca\uff1a<\/strong>UNION \u4e0d\u80fd\u7528\u4e8e\u5217\u51fa\u4e24\u4e2a\u8868\u4e2d\u6240\u6709\u7684country\u3002\u5982\u679c\u4e00\u4e9b\u7f51\u7ad9\u548cAPP\u6765\u81ea\u540c\u4e00\u4e2a\u56fd\u5bb6\uff0c\u6bcf\u4e2a\u56fd\u5bb6\u53ea\u4f1a\u5217\u51fa\u4e00\u6b21\u3002UNION \u53ea\u4f1a\u9009\u53d6\u4e0d\u540c\u7684\u503c\u3002\u8bf7\u4f7f\u7528 UNION ALL \u6765\u9009\u53d6\u91cd\u590d\u7684\u503c\uff01<\/p>\n<h3 id=\"sql-union-all-\u5b9e\u4f8b\">SQL UNION ALL \u5b9e\u4f8b<\/h3>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u4f7f\u7528 UNION ALL \u4ece &#8220;Websites&#8221; \u548c &#8220;apps&#8221; \u8868\u4e2d\u9009\u53d6<strong>\u6240\u6709\u7684<\/strong>country\uff08\u4e5f\u6709\u91cd\u590d\u7684\u503c\uff09\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT country FROM Websites\nUNION ALL\nSELECT country FROM apps\nORDER BY country;\n<\/code><\/pre>\n<p><div class='fancybox-wrapper lazyload-container-unload' data-fancybox='post-images' href='https:\/\/pic.vanforever.com.cn\/MySQL\/20240424\/2024042405.jpg'><img class=\"lazyload lazyload-style-1\" src=\"data:image\/svg+xml;base64,PCEtLUFyZ29uTG9hZGluZy0tPgo8c3ZnIHdpZHRoPSIxIiBoZWlnaHQ9IjEiIHhtbG5zPSJodHRwOi8vd3d3LnczLm9yZy8yMDAwL3N2ZyIgc3Ryb2tlPSIjZmZmZmZmMDAiPjxnPjwvZz4KPC9zdmc+\"  decoding=\"async\" data-original=\"https:\/\/pic.vanforever.com.cn\/MySQL\/20240424\/2024042405.jpg\" src=\"data:image\/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsQAAA7EAZUrDhsAAAANSURBVBhXYzh8+PB\/AAffA0nNPuCLAAAAAElFTkSuQmCC\" \/><\/div><\/p>\n<hr \/>\n<h2 id=\"sql-select-into-\u8bed\u53e5\">SQL SELECT INTO \u8bed\u53e5<\/h2>\n<p>SELECT INTO \u8bed\u53e5\u4ece\u4e00\u4e2a\u8868\u590d\u5236\u6570\u636e\uff0c\u7136\u540e\u628a\u6570\u636e\u63d2\u5165\u5230\u53e6\u4e00\u4e2a\u65b0\u8868\u4e2d\u3002<\/p>\n<blockquote><p><strong>\u6ce8\u610f\uff1a<\/strong><\/p>\n<p>MySQL \u6570\u636e\u5e93\u4e0d\u652f\u6301 SELECT &#8230; INTO \u8bed\u53e5\uff0c\u4f46\u652f\u6301INSERT INTO &#8230; SELECT<\/p>\n<p>\u5f53\u7136\u4f60\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b\u8bed\u53e5\u6765\u62f7\u8d1d\u8868\u7ed3\u6784\u53ca\u6570\u636e\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">CREATE TABLE \u65b0\u8868\nAS\nSELECT * FROM \u65e7\u8868 \n<\/code><\/pre>\n<\/blockquote>\n<hr \/>\n<h2 id=\"sql-insert-into-select-\u8bed\u53e5\">SQL INSERT INTO SELECT \u8bed\u53e5<\/h2>\n<p>INSERT INTO SELECT \u8bed\u53e5\u4ece\u4e00\u4e2a\u8868\u590d\u5236\u6570\u636e\uff0c\u7136\u540e\u628a\u6570\u636e\u63d2\u5165\u5230\u4e00\u4e2a\u5df2\u5b58\u5728\u7684\u8868\u4e2d\u3002\u76ee\u6807\u8868\u4e2d\u4efb\u4f55\u5df2\u5b58\u5728\u7684\u884c\u90fd\u4e0d\u4f1a\u53d7\u5f71\u54cd\u3002<\/p>\n<h3 id=\"sql-insert-into-select-\u8bed\u6cd5\">SQL INSERT INTO SELECT \u8bed\u6cd5<\/h3>\n<p>\u6211\u4eec\u53ef\u4ee5\u4ece\u4e00\u4e2a\u8868\u4e2d\u590d\u5236\u6240\u6709\u7684\u5217\u63d2\u5165\u5230\u53e6\u4e00\u4e2a\u5df2\u5b58\u5728\u7684\u8868\u4e2d\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">INSERT INTO table2\nSELECT FROM table1;\n<\/code><\/pre>\n<p>\u6216\u8005\u6211\u4eec\u53ef\u4ee5\u53ea\u590d\u5236\u6307\u5b9a\u7684\u5217\u63d2\u5165\u5230\u53e6\u4e00\u4e2a\u5df2\u5b58\u5728\u7684\u8868\u4e2d\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">INSERT INTO table2\n(column_name(s))\nSELECT column_name(s)\nFROM table1;\n<\/code><\/pre>\n<h2 id=\"sql-insert-into-select-\u5b9e\u4f8b\">SQL INSERT INTO SELECT \u5b9e\u4f8b<\/h2>\n<p>\u590d\u5236 &#8220;apps&#8221; \u4e2d\u7684\u6570\u636e\u63d2\u5165\u5230 &#8220;Websites&#8221; \u4e2d\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">INSERT INTO Websites (name, country)\nSELECT app_name, country FROM apps;\n<\/code><\/pre>\n<p>\u53ea\u590d id=1 \u7684\u6570\u636e\u5230 &#8220;Websites&#8221; \u4e2d\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">INSERT INTO Websites (name, country)\nSELECT app_name, country FROM apps\nWHERE id=1;\n<\/code><\/pre>\n<p>#<\/p>\n<h2 id=\"sql-create-database-\u8bed\u53e5\">SQL CREATE DATABASE \u8bed\u53e5<\/h2>\n<p>CREATE DATABASE \u8bed\u53e5\u7528\u4e8e\u521b\u5efa\u6570\u636e\u5e93\u3002<\/p>\n<h3 id=\"sql-create-database-\u8bed\u6cd5\">SQL CREATE DATABASE \u8bed\u6cd5<\/h3>\n<pre><code class=\"language-mysql\" lang=\"mysql\">CREATE DATABASE dbname;\n<\/code><\/pre>\n<h3 id=\"sql-create-database-\u5b9e\u4f8b\">SQL CREATE DATABASE \u5b9e\u4f8b<\/h3>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u521b\u5efa\u4e00\u4e2a\u540d\u4e3a &#8220;my_db&#8221; \u7684\u6570\u636e\u5e93\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">CREATE DATABASE my_db;\n<\/code><\/pre>\n<p>\u6570\u636e\u5e93\u8868\u53ef\u4ee5\u901a\u8fc7 CREATE TABLE \u8bed\u53e5\u6765\u6dfb\u52a0\u3002<\/p>\n<hr \/>\n<h2 id=\"sql-create-table-\u8bed\u53e5\">SQL CREATE TABLE \u8bed\u53e5<\/h2>\n<p>CREATE TABLE \u8bed\u53e5\u7528\u4e8e\u521b\u5efa\u6570\u636e\u5e93\u4e2d\u7684\u8868\u3002<\/p>\n<p>\u8868\u7531\u884c\u548c\u5217\u7ec4\u6210\uff0c\u6bcf\u4e2a\u8868\u90fd\u5fc5\u987b\u6709\u4e2a\u8868\u540d\u3002<\/p>\n<h3 id=\"sql-create-table-\u8bed\u6cd5\">SQL CREATE TABLE \u8bed\u6cd5<\/h3>\n<pre><code class=\"language-mysql\" lang=\"mysql\">CREATE TABLE *table_name*\n(\ncolumn_name1 data_type(size),\ncolumn_name2 data_type(size),\ncolumn_name3 data_type(size),\n....\n);\n<\/code><\/pre>\n<p>column_name \u53c2\u6570\u89c4\u5b9a\u8868\u4e2d\u5217\u7684\u540d\u79f0\u3002<\/p>\n<p>data_type \u53c2\u6570\u89c4\u5b9a\u5217\u7684\u6570\u636e\u7c7b\u578b\uff08\u4f8b\u5982 varchar\u3001integer\u3001decimal\u3001date \u7b49\u7b49\uff09\u3002<\/p>\n<p>size \u53c2\u6570\u89c4\u5b9a\u8868\u4e2d\u5217\u7684\u6700\u5927\u957f\u5ea6\u3002<\/p>\n<h3 id=\"sql-create-table-\u5b9e\u4f8b\">SQL CREATE TABLE \u5b9e\u4f8b<\/h3>\n<p>\u73b0\u5728\u6211\u4eec\u60f3\u8981\u521b\u5efa\u4e00\u4e2a\u540d\u4e3a &#8220;Persons&#8221; \u7684\u8868\uff0c\u5305\u542b\u4e94\u5217\uff1aPersonID\u3001LastName\u3001FirstName\u3001Address \u548c City\u3002<\/p>\n<p>\u6211\u4eec\u4f7f\u7528\u4e0b\u9762\u7684 CREATE TABLE \u8bed\u53e5\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">CREATE TABLE Persons\n(\nPersonID int,\nLastName varchar(255),\nFirstName varchar(255),\nAddress varchar(255),\nCity varchar(255)\n);\n<\/code><\/pre>\n<hr \/>\n<h2 id=\"sql-\u7ea6\u675fconstraints\uff09\">SQL \u7ea6\u675f\uff08Constraints\uff09<\/h2>\n<p>SQL \u7ea6\u675f\u7528\u4e8e\u89c4\u5b9a\u8868\u4e2d\u7684\u6570\u636e\u89c4\u5219\u3002<\/p>\n<p>\u5982\u679c\u5b58\u5728\u8fdd\u53cd\u7ea6\u675f\u7684\u6570\u636e\u884c\u4e3a\uff0c\u884c\u4e3a\u4f1a\u88ab\u7ea6\u675f\u7ec8\u6b62\u3002<\/p>\n<p>\u7ea6\u675f\u53ef\u4ee5\u5728\u521b\u5efa\u8868\u65f6\u89c4\u5b9a\uff08\u901a\u8fc7 CREATE TABLE \u8bed\u53e5\uff09\uff0c\u6216\u8005\u5728\u8868\u521b\u5efa\u4e4b\u540e\u89c4\u5b9a\uff08\u901a\u8fc7 ALTER TABLE \u8bed\u53e5\uff09\u3002<\/p>\n<h3 id=\"sql-create-table--constraint-\u8bed\u6cd5\">SQL CREATE TABLE + CONSTRAINT \u8bed\u6cd5<\/h3>\n<pre><code class=\"language-mysql\" lang=\"mysql\">CREATE TABLE table_name\n(\ncolumn_name1 data_type(size) constraint_name,\ncolumn_name2 data_type(size) constraint_name,\ncolumn_name3 data_type(size) constraint_name,\n....\n);\n<\/code><\/pre>\n<p>\u5728 SQL \u4e2d\uff0c\u6211\u4eec\u6709\u5982\u4e0b\u7ea6\u675f\uff1a<\/p>\n<ul>\n<li><strong>NOT NULL<\/strong> &#8211; \u6307\u793a\u67d0\u5217\u4e0d\u80fd\u5b58\u50a8 NULL \u503c\u3002<\/li>\n<li><strong>UNIQUE<\/strong> &#8211; \u4fdd\u8bc1\u67d0\u5217\u7684\u6bcf\u884c\u5fc5\u987b\u6709\u552f\u4e00\u7684\u503c\u3002<\/li>\n<li><strong>PRIMARY KEY<\/strong> &#8211; NOT NULL \u548c UNIQUE \u7684\u7ed3\u5408\u3002\u786e\u4fdd\u67d0\u5217\uff08\u6216\u4e24\u4e2a\u5217\u591a\u4e2a\u5217\u7684\u7ed3\u5408\uff09\u6709\u552f\u4e00\u6807\u8bc6\uff0c\u6709\u52a9\u4e8e\u66f4\u5bb9\u6613\u66f4\u5feb\u901f\u5730\u627e\u5230\u8868\u4e2d\u7684\u4e00\u4e2a\u7279\u5b9a\u7684\u8bb0\u5f55\u3002<\/li>\n<li><strong>FOREIGN KEY<\/strong> &#8211; \u4fdd\u8bc1\u4e00\u4e2a\u8868\u4e2d\u7684\u6570\u636e\u5339\u914d\u53e6\u4e00\u4e2a\u8868\u4e2d\u7684\u503c\u7684\u53c2\u7167\u5b8c\u6574\u6027\u3002<\/li>\n<li><strong>CHECK<\/strong> &#8211; \u4fdd\u8bc1\u5217\u4e2d\u7684\u503c\u7b26\u5408\u6307\u5b9a\u7684\u6761\u4ef6\u3002<\/li>\n<li><strong>DEFAULT<\/strong> &#8211; \u89c4\u5b9a\u6ca1\u6709\u7ed9\u5217\u8d4b\u503c\u65f6\u7684\u9ed8\u8ba4\u503c\u3002<\/li>\n<\/ul>\n<hr \/>\n<h2 id=\"sql-not-null-\u7ea6\u675f\">SQL NOT NULL \u7ea6\u675f<\/h2>\n<p>NOT NULL \u7ea6\u675f\u5f3a\u5236\u5217\u4e0d\u63a5\u53d7 NULL \u503c\u3002<\/p>\n<p>NOT NULL \u7ea6\u675f\u5f3a\u5236\u5b57\u6bb5\u59cb\u7ec8\u5305\u542b\u503c\u3002\u8fd9\u610f\u5473\u7740\uff0c\u5982\u679c\u4e0d\u5411\u5b57\u6bb5\u6dfb\u52a0\u503c\uff0c\u5c31\u65e0\u6cd5\u63d2\u5165\u65b0\u8bb0\u5f55\u6216\u8005\u66f4\u65b0\u8bb0\u5f55\u3002<\/p>\n<p>\u4e0b\u9762\u7684 SQL \u5f3a\u5236 &#8220;ID&#8221; \u5217\u3001 &#8220;LastName&#8221; \u5217\u4ee5\u53ca &#8220;FirstName&#8221; \u5217\u4e0d\u63a5\u53d7 NULL \u503c\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">CREATE TABLE Persons (\n    ID int NOT NULL,\n    LastName varchar(255) NOT NULL,\n    FirstName varchar(255) NOT NULL,\n    Age int\n);\n<\/code><\/pre>\n<h3 id=\"\u6dfb\u52a0-not-null-\u7ea6\u675f\">\u6dfb\u52a0 NOT NULL \u7ea6\u675f<\/h3>\n<p>\u5728\u4e00\u4e2a\u5df2\u521b\u5efa\u7684\u8868\u7684 &#8220;Age&#8221; \u5b57\u6bb5\u4e2d\u6dfb\u52a0 NOT NULL \u7ea6\u675f\u5982\u4e0b\u6240\u793a\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">ALTER TABLE Persons\nMODIFY Age int NOT NULL;\n<\/code><\/pre>\n<h3 id=\"\u5220\u9664-not-null-\u7ea6\u675f\">\u5220\u9664 NOT NULL \u7ea6\u675f<\/h3>\n<p>\u5728\u4e00\u4e2a\u5df2\u521b\u5efa\u7684\u8868\u7684 &#8220;Age&#8221; \u5b57\u6bb5\u4e2d\u5220\u9664 NOT NULL \u7ea6\u675f\u5982\u4e0b\u6240\u793a\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">ALTER TABLE Persons\nMODIFY Age int NULL;\n<\/code><\/pre>\n<hr \/>\n<h2 id=\"sql-unique-\u7ea6\u675f\">SQL UNIQUE \u7ea6\u675f<\/h2>\n<p>UNIQUE \u7ea6\u675f\u552f\u4e00\u6807\u8bc6\u6570\u636e\u5e93\u8868\u4e2d\u7684\u6bcf\u6761\u8bb0\u5f55\u3002<\/p>\n<p>UNIQUE \u548c PRIMARY KEY \u7ea6\u675f\u5747\u4e3a\u5217\u6216\u5217\u96c6\u5408\u63d0\u4f9b\u4e86\u552f\u4e00\u6027\u7684\u4fdd\u8bc1\u3002<\/p>\n<p>PRIMARY KEY \u7ea6\u675f\u62e5\u6709\u81ea\u52a8\u5b9a\u4e49\u7684 UNIQUE \u7ea6\u675f\u3002<\/p>\n<p>\u8bf7\u6ce8\u610f\uff0c\u6bcf\u4e2a\u8868\u53ef\u4ee5\u6709\u591a\u4e2a UNIQUE \u7ea6\u675f\uff0c\u4f46\u662f\u6bcf\u4e2a\u8868\u53ea\u80fd\u6709\u4e00\u4e2a PRIMARY KEY \u7ea6\u675f\u3002<\/p>\n<h3 id=\"create-table-\u65f6\u7684-sql-unique-\u7ea6\u675f\">CREATE TABLE \u65f6\u7684 SQL UNIQUE \u7ea6\u675f<\/h3>\n<p>\u4e0b\u9762\u7684 SQL \u5728 &#8220;Persons&#8221; \u8868\u521b\u5efa\u65f6\u5728 &#8220;P_Id&#8221; \u5217\u4e0a\u521b\u5efa UNIQUE \u7ea6\u675f\uff1a<\/p>\n<p><strong>MySQL\uff1a<\/strong><\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">CREATE TABLE Persons\n(\nP_Id int NOT NULL,\nLastName varchar(255) NOT NULL,\nFirstName varchar(255),\nAddress varchar(255),\nCity varchar(255),\nUNIQUE (P_Id)\n)\n<\/code><\/pre>\n<p>\u5982\u9700\u547d\u540d UNIQUE \u7ea6\u675f\uff0c\u5e76\u5b9a\u4e49\u591a\u4e2a\u5217\u7684 UNIQUE \u7ea6\u675f\uff0c\u8bf7\u4f7f\u7528\u4e0b\u9762\u7684 SQL \u8bed\u6cd5\uff1a<\/p>\n<p><strong>MySQL \/ SQL Server \/ Oracle \/ MS Access\uff1a<\/strong><\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">CREATE TABLE Persons\n(\nP_Id int NOT NULL,\nLastName varchar(255) NOT NULL,\nFirstName varchar(255),\nAddress varchar(255),\nCity varchar(255),\nCONSTRAINT uc_PersonID UNIQUE (P_Id,LastName)\n)\n<\/code><\/pre>\n<h3 id=\"alter-table-\u65f6\u7684-sql-unique-\u7ea6\u675f\">ALTER TABLE \u65f6\u7684 SQL UNIQUE \u7ea6\u675f<\/h3>\n<p>\u5f53\u8868\u5df2\u88ab\u521b\u5efa\u65f6\uff0c\u5982\u9700\u5728 &#8220;P_Id&#8221; \u5217\u521b\u5efa UNIQUE \u7ea6\u675f\uff0c\u8bf7\u4f7f\u7528\u4e0b\u9762\u7684 SQL\uff1a<\/p>\n<p><strong>MySQL \/ SQL Server \/ Oracle \/ MS Access\uff1a<\/strong><\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">ALTER TABLE Persons\nADD UNIQUE (P_Id)\n<\/code><\/pre>\n<p>\u5982\u9700\u547d\u540d UNIQUE \u7ea6\u675f\uff0c\u5e76\u5b9a\u4e49\u591a\u4e2a\u5217\u7684 UNIQUE \u7ea6\u675f\uff0c\u8bf7\u4f7f\u7528\u4e0b\u9762\u7684 SQL \u8bed\u6cd5\uff1a<\/p>\n<p><strong>MySQL \/ SQL Server \/ Oracle \/ MS Access\uff1a<\/strong><\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">ALTER TABLE Persons\nADD CONSTRAINT uc_PersonID UNIQUE (P_Id,LastName)\n<\/code><\/pre>\n<h3 id=\"\u64a4\u9500-unique-\u7ea6\u675f\">\u64a4\u9500 UNIQUE \u7ea6\u675f<\/h3>\n<p>\u5982\u9700\u64a4\u9500 UNIQUE \u7ea6\u675f\uff0c\u8bf7\u4f7f\u7528\u4e0b\u9762\u7684 SQL\uff1a<\/p>\n<p><strong>MySQL\uff1a<\/strong><\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">ALTER TABLE Persons\nDROP INDEX uc_PersonID\n<\/code><\/pre>\n<hr \/>\n<h2 id=\"sql-primary-key-\u7ea6\u675f\">SQL PRIMARY KEY \u7ea6\u675f<\/h2>\n<p>PRIMARY KEY \u7ea6\u675f\u552f\u4e00\u6807\u8bc6\u6570\u636e\u5e93\u8868\u4e2d\u7684\u6bcf\u6761\u8bb0\u5f55\u3002<\/p>\n<p>\u4e3b\u952e\u5fc5\u987b\u5305\u542b\u552f\u4e00\u7684\u503c\u3002<\/p>\n<p>\u4e3b\u952e\u5217\u4e0d\u80fd\u5305\u542b NULL \u503c\u3002<\/p>\n<p>\u6bcf\u4e2a\u8868\u90fd\u5e94\u8be5\u6709\u4e00\u4e2a\u4e3b\u952e\uff0c\u5e76\u4e14\u6bcf\u4e2a\u8868\u53ea\u80fd\u6709\u4e00\u4e2a\u4e3b\u952e\u3002<\/p>\n<h3 id=\"create-table-\u65f6\u7684-sql-primary-key-\u7ea6\u675f\">CREATE TABLE \u65f6\u7684 SQL PRIMARY KEY \u7ea6\u675f<\/h3>\n<p>\u4e0b\u9762\u7684 SQL \u5728 &#8220;Persons&#8221; \u8868\u521b\u5efa\u65f6\u5728 &#8220;P_Id&#8221; \u5217\u4e0a\u521b\u5efa PRIMARY KEY \u7ea6\u675f\uff1a<\/p>\n<p><strong>MySQL\uff1a<\/strong><\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">CREATE TABLE Persons\n(\nP_Id int NOT NULL,\nLastName varchar(255) NOT NULL,\nFirstName varchar(255),\nAddress varchar(255),\nCity varchar(255),\nPRIMARY KEY (P_Id)\n)\n<\/code><\/pre>\n<p>\u5982\u9700\u547d\u540d PRIMARY KEY \u7ea6\u675f\uff0c\u5e76\u5b9a\u4e49\u591a\u4e2a\u5217\u7684 PRIMARY KEY \u7ea6\u675f\uff0c\u8bf7\u4f7f\u7528\u4e0b\u9762\u7684 SQL \u8bed\u6cd5\uff1a<\/p>\n<p><strong>MySQL \/ SQL Server \/ Oracle \/ MS Access\uff1a<\/strong><\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">CREATE TABLE Persons\n(\nP_Id int NOT NULL,\nLastName varchar(255) NOT NULL,\nFirstName varchar(255),\nAddress varchar(255),\nCity varchar(255),\nCONSTRAINT pk_PersonID PRIMARY KEY (P_Id,LastName)\n)\n<\/code><\/pre>\n<p><strong>\u6ce8\u91ca\uff1a<\/strong>\u5728\u4e0a\u9762\u7684\u5b9e\u4f8b\u4e2d\uff0c\u53ea\u6709\u4e00\u4e2a\u4e3b\u952e PRIMARY KEY\uff08pk_PersonID\uff09\u3002\u7136\u800c\uff0cpk_PersonID \u7684\u503c\u662f\u7531\u4e24\u4e2a\u5217\uff08P_Id \u548c LastName\uff09\u7ec4\u6210\u7684\u3002<\/p>\n<h3 id=\"alter-table-\u65f6\u7684-sql-primary-key-\u7ea6\u675f\">ALTER TABLE \u65f6\u7684 SQL PRIMARY KEY \u7ea6\u675f<\/h3>\n<p>\u5f53\u8868\u5df2\u88ab\u521b\u5efa\u65f6\uff0c\u5982\u9700\u5728 &#8220;P_Id&#8221; \u5217\u521b\u5efa PRIMARY KEY \u7ea6\u675f\uff0c\u8bf7\u4f7f\u7528\u4e0b\u9762\u7684 SQL\uff1a<\/p>\n<p><strong>MySQL \/ SQL Server \/ Oracle \/ MS Access\uff1a<\/strong><\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">ALTER TABLE Persons\nADD PRIMARY KEY (P_Id)\n<\/code><\/pre>\n<p>\u5982\u9700\u547d\u540d PRIMARY KEY \u7ea6\u675f\uff0c\u5e76\u5b9a\u4e49\u591a\u4e2a\u5217\u7684 PRIMARY KEY \u7ea6\u675f\uff0c\u8bf7\u4f7f\u7528\u4e0b\u9762\u7684 SQL \u8bed\u6cd5\uff1a<\/p>\n<p><strong>MySQL \/ SQL Server \/ Oracle \/ MS Access\uff1a<\/strong><\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">ALTER TABLE Persons\nADD CONSTRAINT pk_PersonID PRIMARY KEY (P_Id,LastName)\n<\/code><\/pre>\n<p><strong>\u6ce8\u91ca\uff1a<\/strong>\u5982\u679c\u60a8\u4f7f\u7528 ALTER TABLE \u8bed\u53e5\u6dfb\u52a0\u4e3b\u952e\uff0c\u5fc5\u987b\u628a\u4e3b\u952e\u5217\u58f0\u660e\u4e3a\u4e0d\u5305\u542b NULL \u503c\uff08\u5728\u8868\u9996\u6b21\u521b\u5efa\u65f6\uff09\u3002<\/p>\n<h3 id=\"\u64a4\u9500-primary-key-\u7ea6\u675f\">\u64a4\u9500 PRIMARY KEY \u7ea6\u675f<\/h3>\n<p>\u5982\u9700\u64a4\u9500 PRIMARY KEY \u7ea6\u675f\uff0c\u8bf7\u4f7f\u7528\u4e0b\u9762\u7684 SQL\uff1a<\/p>\n<p><strong>MySQL\uff1a<\/strong><\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">ALTER TABLE Persons\nDROP PRIMARY KEY\n<\/code><\/pre>\n<hr \/>\n<h2 id=\"sql-foreign-key-\u7ea6\u675f\">SQL FOREIGN KEY \u7ea6\u675f<\/h2>\n<p>\u4e00\u4e2a\u8868\u4e2d\u7684 FOREIGN KEY \u6307\u5411\u53e6\u4e00\u4e2a\u8868\u4e2d\u7684 UNIQUE KEY(\u552f\u4e00\u7ea6\u675f\u7684\u952e)\u3002<\/p>\n<p>\u8ba9\u6211\u4eec\u901a\u8fc7\u4e00\u4e2a\u5b9e\u4f8b\u6765\u89e3\u91ca\u5916\u952e\u3002\u8bf7\u770b\u4e0b\u9762\u4e24\u4e2a\u8868\uff1a<\/p>\n<p>&#8220;Persons&#8221; \u8868\uff1a<\/p>\n<figure class=\"table-figure\">\n<table>\n<thead>\n<tr>\n<th style=\"text-align: left;\">P_Id<\/th>\n<th style=\"text-align: left;\">LastName<\/th>\n<th style=\"text-align: left;\">FirstName<\/th>\n<th style=\"text-align: left;\">Address<\/th>\n<th style=\"text-align: left;\">City<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td style=\"text-align: left;\">1<\/td>\n<td style=\"text-align: left;\">Hansen<\/td>\n<td style=\"text-align: left;\">Ola<\/td>\n<td style=\"text-align: left;\">Timoteivn 10<\/td>\n<td style=\"text-align: left;\">Sandnes<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">2<\/td>\n<td style=\"text-align: left;\">Svendson<\/td>\n<td style=\"text-align: left;\">Tove<\/td>\n<td style=\"text-align: left;\">Borgvn 23<\/td>\n<td style=\"text-align: left;\">Sandnes<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">3<\/td>\n<td style=\"text-align: left;\">Pettersen<\/td>\n<td style=\"text-align: left;\">Kari<\/td>\n<td style=\"text-align: left;\">Storgt 20<\/td>\n<td style=\"text-align: left;\">Stavanger<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<p>&#8220;Orders&#8221; \u8868\uff1a<\/p>\n<figure class=\"table-figure\">\n<table>\n<thead>\n<tr>\n<th style=\"text-align: left;\">O_Id<\/th>\n<th style=\"text-align: left;\">OrderNo<\/th>\n<th style=\"text-align: left;\">P_Id<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td style=\"text-align: left;\">1<\/td>\n<td style=\"text-align: left;\">77895<\/td>\n<td style=\"text-align: left;\">3<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">2<\/td>\n<td style=\"text-align: left;\">44678<\/td>\n<td style=\"text-align: left;\">3<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">3<\/td>\n<td style=\"text-align: left;\">22456<\/td>\n<td style=\"text-align: left;\">2<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">4<\/td>\n<td style=\"text-align: left;\">24562<\/td>\n<td style=\"text-align: left;\">1<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<p>\u8bf7\u6ce8\u610f\uff0c&#8221;Orders&#8221; \u8868\u4e2d\u7684 &#8220;P_Id&#8221; \u5217\u6307\u5411 &#8220;Persons&#8221; \u8868\u4e2d\u7684 &#8220;P_Id&#8221; \u5217\u3002<\/p>\n<p>&#8220;Persons&#8221; \u8868\u4e2d\u7684 &#8220;P_Id&#8221; \u5217\u662f &#8220;Persons&#8221; \u8868\u4e2d\u7684 PRIMARY KEY\u3002<\/p>\n<p>&#8220;Orders&#8221; \u8868\u4e2d\u7684 &#8220;P_Id&#8221; \u5217\u662f &#8220;Orders&#8221; \u8868\u4e2d\u7684 FOREIGN KEY\u3002<\/p>\n<p>FOREIGN KEY \u7ea6\u675f\u7528\u4e8e\u9884\u9632\u7834\u574f\u8868\u4e4b\u95f4\u8fde\u63a5\u7684\u884c\u4e3a\u3002<\/p>\n<p>FOREIGN KEY \u7ea6\u675f\u4e5f\u80fd\u9632\u6b62\u975e\u6cd5\u6570\u636e\u63d2\u5165\u5916\u952e\u5217\uff0c\u56e0\u4e3a\u5b83\u5fc5\u987b\u662f\u5b83\u6307\u5411\u7684\u90a3\u4e2a\u8868\u4e2d\u7684\u503c\u4e4b\u4e00\u3002<\/p>\n<h3 id=\"create-table-\u65f6\u7684-sql-foreign-key-\u7ea6\u675f\">CREATE TABLE \u65f6\u7684 SQL FOREIGN KEY \u7ea6\u675f<\/h3>\n<p>\u4e0b\u9762\u7684 SQL \u5728 &#8220;Orders&#8221; \u8868\u521b\u5efa\u65f6\u5728 &#8220;P_Id&#8221; \u5217\u4e0a\u521b\u5efa FOREIGN KEY \u7ea6\u675f\uff1a<\/p>\n<p><strong>MySQL\uff1a<\/strong><\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">CREATE TABLE Orders\n(\nO_Id int NOT NULL,\nOrderNo int NOT NULL,\nP_Id int,\nPRIMARY KEY (O_Id),\nFOREIGN KEY (P_Id) REFERENCES Persons(P_Id)\n<\/code><\/pre>\n<p>\u5982\u9700\u547d\u540d FOREIGN KEY \u7ea6\u675f\uff0c\u5e76\u5b9a\u4e49\u591a\u4e2a\u5217\u7684 FOREIGN KEY \u7ea6\u675f\uff0c\u8bf7\u4f7f\u7528\u4e0b\u9762\u7684 SQL \u8bed\u6cd5\uff1a<\/p>\n<p><strong>MySQL \/ SQL Server \/ Oracle \/ MS Access\uff1a<\/strong><\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">CREATE TABLE Orders\n(\nO_Id int NOT NULL,\nOrderNo int NOT NULL,\nP_Id int,\nPRIMARY KEY (O_Id),\nCONSTRAINT fk_PerOrders FOREIGN KEY (P_Id)\nREFERENCES Persons(P_Id)\n)\n<\/code><\/pre>\n<h3 id=\"alter-table-\u65f6\u7684-sql-foreign-key-\u7ea6\u675f\">ALTER TABLE \u65f6\u7684 SQL FOREIGN KEY \u7ea6\u675f<\/h3>\n<p>\u5f53 &#8220;Orders&#8221; \u8868\u5df2\u88ab\u521b\u5efa\u65f6\uff0c\u5982\u9700\u5728 &#8220;P_Id&#8221; \u5217\u521b\u5efa FOREIGN KEY \u7ea6\u675f\uff0c\u8bf7\u4f7f\u7528\u4e0b\u9762\u7684 SQL\uff1a<\/p>\n<p><strong>MySQL \/ SQL Server \/ Oracle \/ MS Access\uff1a<\/strong><\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">ALTER TABLE Orders\nADD FOREIGN KEY (P_Id)\nREFERENCES Persons(P_Id)\n<\/code><\/pre>\n<p>\u5982\u9700\u547d\u540d FOREIGN KEY \u7ea6\u675f\uff0c\u5e76\u5b9a\u4e49\u591a\u4e2a\u5217\u7684 FOREIGN KEY \u7ea6\u675f\uff0c\u8bf7\u4f7f\u7528\u4e0b\u9762\u7684 SQL \u8bed\u6cd5\uff1a<\/p>\n<p><strong>MySQL \/ SQL Server \/ Oracle \/ MS Access\uff1a<\/strong><\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">ALTER TABLE Orders\nADD CONSTRAINT fk_PerOrders\nFOREIGN KEY (P_Id)\nREFERENCES Persons(P_Id)\n<\/code><\/pre>\n<h3 id=\"\u64a4\u9500-foreign-key-\u7ea6\u675f\">\u64a4\u9500 FOREIGN KEY \u7ea6\u675f<\/h3>\n<p>\u5982\u9700\u64a4\u9500 FOREIGN KEY \u7ea6\u675f\uff0c\u8bf7\u4f7f\u7528\u4e0b\u9762\u7684 SQL\uff1a<\/p>\n<p><strong>MySQL\uff1a<\/strong><\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">ALTER TABLE Orders\nDROP FOREIGN KEY fk_PerOrders\n<\/code><\/pre>\n<hr \/>\n<h2 id=\"sql-check-\u7ea6\u675f\">SQL CHECK \u7ea6\u675f<\/h2>\n<p>CHECK \u7ea6\u675f\u7528\u4e8e\u9650\u5236\u5217\u4e2d\u7684\u503c\u7684\u8303\u56f4\u3002<\/p>\n<p>\u5982\u679c\u5bf9\u5355\u4e2a\u5217\u5b9a\u4e49 CHECK \u7ea6\u675f\uff0c\u90a3\u4e48\u8be5\u5217\u53ea\u5141\u8bb8\u7279\u5b9a\u7684\u503c\u3002<\/p>\n<p>\u5982\u679c\u5bf9\u4e00\u4e2a\u8868\u5b9a\u4e49 CHECK \u7ea6\u675f\uff0c\u90a3\u4e48\u6b64\u7ea6\u675f\u4f1a\u57fa\u4e8e\u884c\u4e2d\u5176\u4ed6\u5217\u7684\u503c\u5728\u7279\u5b9a\u7684\u5217\u4e2d\u5bf9\u503c\u8fdb\u884c\u9650\u5236\u3002<\/p>\n<hr \/>\n<h2 id=\"create-table-\u65f6\u7684-sql-check-\u7ea6\u675f\">CREATE TABLE \u65f6\u7684 SQL CHECK \u7ea6\u675f<\/h2>\n<p>\u4e0b\u9762\u7684 SQL \u5728 &#8220;Persons&#8221; \u8868\u521b\u5efa\u65f6\u5728 &#8220;P_Id&#8221; \u5217\u4e0a\u521b\u5efa CHECK \u7ea6\u675f\u3002CHECK \u7ea6\u675f\u89c4\u5b9a &#8220;P_Id&#8221; \u5217\u5fc5\u987b\u53ea\u5305\u542b\u5927\u4e8e 0 \u7684\u6574\u6570\u3002<\/p>\n<p><strong>MySQL\uff1a<\/strong><\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">CREATE TABLE Persons\n(\nP_Id int NOT NULL,\nLastName varchar(255) NOT NULL,\nFirstName varchar(255),\nAddress varchar(255),\nCity varchar(255),\nCHECK (P_Id&gt;0)\n)\n<\/code><\/pre>\n<p>\u5982\u9700\u547d\u540d CHECK \u7ea6\u675f\uff0c\u5e76\u5b9a\u4e49\u591a\u4e2a\u5217\u7684 CHECK \u7ea6\u675f\uff0c\u8bf7\u4f7f\u7528\u4e0b\u9762\u7684 SQL \u8bed\u6cd5\uff1a<\/p>\n<p><strong>MySQL \/ SQL Server \/ Oracle \/ MS Access\uff1a<\/strong><\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">CREATE TABLE Persons\n(\nP_Id int NOT NULL,\nLastName varchar(255) NOT NULL,\nFirstName varchar(255),\nAddress varchar(255),\nCity varchar(255),\nCONSTRAINT chk_Person CHECK (P_Id&gt;0 AND City='Sandnes')\n)\n<\/code><\/pre>\n<h3 id=\"alter-table-\u65f6\u7684-sql-check-\u7ea6\u675f\">ALTER TABLE \u65f6\u7684 SQL CHECK \u7ea6\u675f<\/h3>\n<p>\u5f53\u8868\u5df2\u88ab\u521b\u5efa\u65f6\uff0c\u5982\u9700\u5728 &#8220;P_Id&#8221; \u5217\u521b\u5efa CHECK \u7ea6\u675f\uff0c\u8bf7\u4f7f\u7528\u4e0b\u9762\u7684 SQL\uff1a<\/p>\n<p><strong>MySQL \/ SQL Server \/ Oracle \/ MS Access:<\/strong><\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">ALTER TABLE Persons\nADD CHECK (P_Id&gt;0)\n<\/code><\/pre>\n<p>\u5982\u9700\u547d\u540d CHECK \u7ea6\u675f\uff0c\u5e76\u5b9a\u4e49\u591a\u4e2a\u5217\u7684 CHECK \u7ea6\u675f\uff0c\u8bf7\u4f7f\u7528\u4e0b\u9762\u7684 SQL \u8bed\u6cd5\uff1a<\/p>\n<p><strong>MySQL \/ SQL Server \/ Oracle \/ MS Access\uff1a<\/strong><\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">ALTER TABLE Persons\nADD CONSTRAINT chk_Person CHECK (P_Id&gt;0 AND City='Sandnes')\n<\/code><\/pre>\n<h3 id=\"\u64a4\u9500-check-\u7ea6\u675f\">\u64a4\u9500 CHECK \u7ea6\u675f<\/h3>\n<p>\u5982\u9700\u64a4\u9500 CHECK \u7ea6\u675f\uff0c\u8bf7\u4f7f\u7528\u4e0b\u9762\u7684 SQL\uff1a<\/p>\n<p><strong>MySQL\uff1a<\/strong><\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">ALTER TABLE Persons\nDROP CHECK chk_Person\n<\/code><\/pre>\n<hr \/>\n<h2 id=\"sql-default-\u7ea6\u675f\">SQL DEFAULT \u7ea6\u675f<\/h2>\n<p>DEFAULT \u7ea6\u675f\u7528\u4e8e\u5411\u5217\u4e2d\u63d2\u5165\u9ed8\u8ba4\u503c\u3002<\/p>\n<p>\u5982\u679c\u6ca1\u6709\u89c4\u5b9a\u5176\u4ed6\u7684\u503c\uff0c\u90a3\u4e48\u4f1a\u5c06\u9ed8\u8ba4\u503c\u6dfb\u52a0\u5230\u6240\u6709\u7684\u65b0\u8bb0\u5f55\u3002<\/p>\n<h3 id=\"create-table-\u65f6\u7684-sql-default-\u7ea6\u675f\">CREATE TABLE \u65f6\u7684 SQL DEFAULT \u7ea6\u675f<\/h3>\n<p>\u4e0b\u9762\u7684 SQL \u5728 &#8220;Persons&#8221; \u8868\u521b\u5efa\u65f6\u5728 &#8220;City&#8221; \u5217\u4e0a\u521b\u5efa DEFAULT \u7ea6\u675f\uff1a<\/p>\n<p><strong>My SQL \/ SQL Server \/ Oracle \/ MS Access\uff1a<\/strong><\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">CREATE TABLE Persons\n(\n    P_Id int NOT NULL,\n    LastName varchar(255) NOT NULL,\n    FirstName varchar(255),\n    Address varchar(255),\n    City varchar(255) DEFAULT 'Sandnes'\n)\n<\/code><\/pre>\n<p>\u901a\u8fc7\u4f7f\u7528\u7c7b\u4f3c GETDATE() \u8fd9\u6837\u7684\u51fd\u6570\uff0cDEFAULT \u7ea6\u675f\u4e5f\u53ef\u4ee5\u7528\u4e8e\u63d2\u5165\u7cfb\u7edf\u503c\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">CREATE TABLE Orders\n(\n    O_Id int NOT NULL,\n    OrderNo int NOT NULL,\n    P_Id int,\n    OrderDate date DEFAULT GETDATE()\n)\n<\/code><\/pre>\n<h3 id=\"alter-table-\u65f6\u7684-sql-default-\u7ea6\u675f\">ALTER TABLE \u65f6\u7684 SQL DEFAULT \u7ea6\u675f<\/h3>\n<p>\u5f53\u8868\u5df2\u88ab\u521b\u5efa\u65f6\uff0c\u5982\u9700\u5728 &#8220;City&#8221; \u5217\u521b\u5efa DEFAULT \u7ea6\u675f\uff0c\u8bf7\u4f7f\u7528\u4e0b\u9762\u7684 SQL\uff1a<\/p>\n<p><strong>MySQL\uff1a<\/strong><\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">ALTER TABLE Persons\nALTER City SET DEFAULT 'SANDNES'\n<\/code><\/pre>\n<h3 id=\"\u64a4\u9500-default-\u7ea6\u675f\">\u64a4\u9500 DEFAULT \u7ea6\u675f<\/h3>\n<p>\u5982\u9700\u64a4\u9500 DEFAULT \u7ea6\u675f\uff0c\u8bf7\u4f7f\u7528\u4e0b\u9762\u7684 SQL\uff1a<\/p>\n<p><strong>MySQL\uff1a<\/strong><\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">ALTER TABLE Persons\nALTER City DROP DEFAULT\n<\/code><\/pre>\n<hr \/>\n<h2 id=\"sql-create-index-\u8bed\u53e5\">SQL CREATE INDEX \u8bed\u53e5<\/h2>\n<p>CREATE INDEX \u8bed\u53e5\u7528\u4e8e\u5728\u8868\u4e2d\u521b\u5efa\u7d22\u5f15\u3002<\/p>\n<p>\u5728\u4e0d\u8bfb\u53d6\u6574\u4e2a\u8868\u7684\u60c5\u51b5\u4e0b\uff0c\u7d22\u5f15\u4f7f\u6570\u636e\u5e93\u5e94\u7528\u7a0b\u5e8f\u53ef\u4ee5\u66f4\u5feb\u5730\u67e5\u627e\u6570\u636e\u3002<\/p>\n<h3 id=\"\u7d22\u5f15\">\u7d22\u5f15<\/h3>\n<p>\u60a8\u53ef\u4ee5\u5728\u8868\u4e2d\u521b\u5efa\u7d22\u5f15\uff0c\u4ee5\u4fbf\u66f4\u52a0\u5feb\u901f\u9ad8\u6548\u5730\u67e5\u8be2\u6570\u636e\u3002<\/p>\n<p>\u7528\u6237\u65e0\u6cd5\u770b\u5230\u7d22\u5f15\uff0c\u5b83\u4eec\u53ea\u80fd\u88ab\u7528\u6765\u52a0\u901f\u641c\u7d22\/\u67e5\u8be2\u3002<\/p>\n<p><strong>\u6ce8\u91ca\uff1a<\/strong>\u66f4\u65b0\u4e00\u4e2a\u5305\u542b\u7d22\u5f15\u7684\u8868\u9700\u8981\u6bd4\u66f4\u65b0\u4e00\u4e2a\u6ca1\u6709\u7d22\u5f15\u7684\u8868\u82b1\u8d39\u66f4\u591a\u7684\u65f6\u95f4\uff0c\u8fd9\u662f\u7531\u4e8e\u7d22\u5f15\u672c\u8eab\u4e5f\u9700\u8981\u66f4\u65b0\u3002\u56e0\u6b64\uff0c\u7406\u60f3\u7684\u505a\u6cd5\u662f\u4ec5\u4ec5\u5728\u5e38\u5e38\u88ab\u641c\u7d22\u7684\u5217\uff08\u4ee5\u53ca\u8868\uff09\u4e0a\u9762\u521b\u5efa\u7d22\u5f15\u3002<\/p>\n<h3 id=\"sql-create-index-\u8bed\u6cd5\">SQL CREATE INDEX \u8bed\u6cd5<\/h3>\n<p>\u5728\u8868\u4e0a\u521b\u5efa\u4e00\u4e2a\u7b80\u5355\u7684\u7d22\u5f15\u3002\u5141\u8bb8\u4f7f\u7528\u91cd\u590d\u7684\u503c\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">CREATE INDEX index_name\nON table_name (column_name)\n<\/code><\/pre>\n<h3 id=\"sql-create-unique-index-\u8bed\u6cd5\">SQL CREATE UNIQUE INDEX \u8bed\u6cd5<\/h3>\n<p>\u5728\u8868\u4e0a\u521b\u5efa\u4e00\u4e2a\u552f\u4e00\u7684\u7d22\u5f15\u3002\u4e0d\u5141\u8bb8\u4f7f\u7528\u91cd\u590d\u7684\u503c\uff1a\u552f\u4e00\u7684\u7d22\u5f15\u610f\u5473\u7740\u4e24\u4e2a\u884c\u4e0d\u80fd\u62e5\u6709\u76f8\u540c\u7684\u7d22\u5f15\u503c\u3002Creates a unique index on a table. Duplicate values are not allowed:<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">CREATE UNIQUE INDEX index_name\nON table_name (column_name)\n<\/code><\/pre>\n<p><strong>\u6ce8\u91ca\uff1a<\/strong>\u7528\u4e8e\u521b\u5efa\u7d22\u5f15\u7684\u8bed\u6cd5\u5728\u4e0d\u540c\u7684\u6570\u636e\u5e93\u4e2d\u4e0d\u4e00\u6837\u3002\u56e0\u6b64\uff0c\u68c0\u67e5\u60a8\u7684\u6570\u636e\u5e93\u4e2d\u521b\u5efa\u7d22\u5f15\u7684\u8bed\u6cd5\u3002<\/p>\n<h3 id=\"create-index-\u5b9e\u4f8b\">CREATE INDEX \u5b9e\u4f8b<\/h3>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u5728 &#8220;Persons&#8221; \u8868\u7684 &#8220;LastName&#8221; \u5217\u4e0a\u521b\u5efa\u4e00\u4e2a\u540d\u4e3a &#8220;PIndex&#8221; \u7684\u7d22\u5f15\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">CREATE INDEX PIndex\nON Persons (LastName)\n<\/code><\/pre>\n<p>\u5982\u679c\u60a8\u5e0c\u671b\u7d22\u5f15\u4e0d\u6b62\u4e00\u4e2a\u5217\uff0c\u60a8\u53ef\u4ee5\u5728\u62ec\u53f7\u4e2d\u5217\u51fa\u8fd9\u4e9b\u5217\u7684\u540d\u79f0\uff0c\u7528\u9017\u53f7\u9694\u5f00\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">CREATE INDEX PIndex\nON Persons (LastName, FirstName)\n<\/code><\/pre>\n<hr \/>\n<h2 id=\"drop-index-\u8bed\u53e5\">DROP INDEX \u8bed\u53e5<\/h2>\n<p>\u7d22\u5f15\u662f\u4e00\u79cd\u4f18\u5316\u6570\u636e\u5e93\u67e5\u8be2\u6027\u80fd\u7684\u7ed3\u6784\uff0c\u4f46\u6709\u65f6\u5019\u53ef\u80fd\u9700\u8981\u5220\u9664\u67d0\u4e2a\u7d22\u5f15\uff0c\u4f8b\u5982\u5f53\u7d22\u5f15\u4e0d\u518d\u9700\u8981\u6216\u9700\u8981\u66ff\u6362\u4e3a\u65b0\u7684\u7d22\u5f15\u65f6\u3002<\/p>\n<p>DROP INDEX \u8bed\u53e5\u7528\u4e8e\u5220\u9664\u8868\u4e2d\u7684\u7d22\u5f15\u3002<\/p>\n<h3 id=\"\u8bed\u6cd5\u683c\u5f0f\">\u8bed\u6cd5\u683c\u5f0f\uff1a<\/h3>\n<pre><code class=\"language-mysql\" lang=\"mysql\">DROP INDEX [IF EXISTS] index_name\nON TABLE_NAME;\n<\/code><\/pre>\n<p><strong>\u53c2\u6570\u8bf4\u660e\uff1a<\/strong><\/p>\n<ul>\n<li><code>DROP INDEX<\/code>\uff1a\u8868\u793a\u8981\u5220\u9664\u7d22\u5f15\u7684\u64cd\u4f5c\u3002<\/li>\n<li><code>IF EXISTS<\/code>\uff1a\u662f\u4e00\u4e2a\u53ef\u9009\u7684\u5b50\u53e5\uff0c\u7528\u4e8e\u68c0\u67e5\u7d22\u5f15\u662f\u5426\u5b58\u5728\u3002\u5982\u679c\u5b58\u5728\uff0c\u5c31\u6267\u884c\u5220\u9664\u64cd\u4f5c\uff1b\u5982\u679c\u4e0d\u5b58\u5728\uff0c\u4e0d\u4f1a\u62a5\u9519\u3002<\/li>\n<li><code>index_name<\/code>\uff1a\u8981\u5220\u9664\u7684\u7d22\u5f15\u7684\u540d\u79f0\u3002<\/li>\n<li><code>ON table_name<\/code>\uff1a\u6307\u5b9a\u5305\u542b\u8981\u5220\u9664\u7d22\u5f15\u7684\u8868\u7684\u540d\u79f0\u3002<\/li>\n<\/ul>\n<p>\u4ee5\u4e0b\u662f\u4e00\u4e2a\u7b80\u5355\u7684\u4f8b\u5b50\uff0c\u5047\u8bbe\u6709\u4e00\u4e2a\u540d\u4e3a idx_example \u7684\u7d22\u5f15\u8981\u4ece\u540d\u4e3a my_table \u7684\u8868\u4e2d\u5220\u9664\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">DROP INDEX IF EXISTS idx_example\nON my_table;\n<\/code><\/pre>\n<p>\u8bf7\u6ce8\u610f\uff0c\u5220\u9664\u7d22\u5f15\u53ef\u80fd\u4f1a\u5f71\u54cd\u6570\u636e\u5e93\u7684\u67e5\u8be2\u6027\u80fd\uff0c\u56e0\u6b64\u5728\u6267\u884c\u6b64\u7c7b\u64cd\u4f5c\u4e4b\u524d\uff0c\u8bf7\u786e\u4fdd\u4e86\u89e3\u5176\u5bf9\u6570\u636e\u5e93\u7684\u5f71\u54cd\uff0c\u5e76\u6839\u636e\u5b9e\u9645\u9700\u6c42\u8fdb\u884c\u64cd\u4f5c\u3002<\/p>\n<h3 id=\"drop-table-\u8bed\u53e5\">DROP TABLE \u8bed\u53e5<\/h3>\n<p>DROP TABLE \u8bed\u53e5\u7528\u4e8e\u5220\u9664\u8868\u3002<\/p>\n<p>\u5220\u9664\u8868\u5c06\u540c\u65f6\u5220\u9664\u8868\u7684\u7ed3\u6784\u4ee5\u53ca\u5b58\u50a8\u5728\u5176\u4e2d\u7684\u6240\u6709\u6570\u636e\u3002\u56e0\u6b64\uff0c\u5728\u6267\u884cDROP TABLE\u8bed\u53e5\u4e4b\u524d\uff0c\u8bf7\u786e\u4fdd\u60a8\u771f\u7684\u5e0c\u671b\u6c38\u4e45\u5220\u9664\u8868\u53ca\u5176\u6240\u6709\u6570\u636e\uff0c\u56e0\u4e3a\u6b64\u64cd\u4f5c\u662f\u4e0d\u53ef\u9006\u7684\u3002<\/p>\n<h3 id=\"\u8bed\u6cd5\u683c\u5f0f-2\">\u8bed\u6cd5\u683c\u5f0f\uff1a<\/h3>\n<pre><code class=\"language-mysql\" lang=\"mysql\">DROP TABLE [IF EXISTS] TABLE_NAME;\n<\/code><\/pre>\n<p><strong>\u53c2\u6570\u8bf4\u660e\uff1a<\/strong><\/p>\n<ul>\n<li><code>DROP TABLE<\/code>\uff1a\u8868\u793a\u5220\u9664\u8868\u7684\u64cd\u4f5c\u3002<\/li>\n<li><code>IF EXISTS<\/code>\uff1a\u662f\u4e00\u4e2a\u53ef\u9009\u7684\u5b50\u53e5\uff0c\u7528\u4e8e\u68c0\u67e5\u8868\u662f\u5426\u5b58\u5728\u3002\u5982\u679c\u5b58\u5728\uff0c\u6267\u884c\u5220\u9664\u64cd\u4f5c\uff1b\u5982\u679c\u4e0d\u5b58\u5728\uff0c\u4e0d\u4f1a\u62a5\u9519\u3002<\/li>\n<li><code>table_name<\/code>\uff1a\u8981\u5220\u9664\u7684\u8868\u7684\u540d\u79f0\u3002<\/li>\n<\/ul>\n<p>\u4ee5\u4e0b\u662f\u4e00\u4e2a\u7b80\u5355\u7684\u4f8b\u5b50\uff0c\u5047\u8bbe\u8981\u5220\u9664\u540d\u4e3a my_table \u7684\u8868\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">DROP TABLE IF EXISTS my_table;\n<\/code><\/pre>\n<p>\u8bf7\u6ce8\u610f\uff0c\u6267\u884cDROP TABLE\u5c06\u6c38\u4e45\u5220\u9664\u8868\u548c\u5176\u6240\u6709\u6570\u636e\u3002\u5728\u6267\u884c\u6b64\u7c7b\u64cd\u4f5c\u4e4b\u524d\uff0c\u8bf7\u786e\u4fdd\u60a8\u5df2\u5907\u4efd\u91cd\u8981\u7684\u6570\u636e\uff0c\u5e76\u4e14\u60a8\u6709\u5220\u9664\u8868\u7684\u6743\u9650\u3002<\/p>\n<h3 id=\"drop-database-\u8bed\u53e5\">DROP DATABASE \u8bed\u53e5<\/h3>\n<p>DROP DATABASE \u8bed\u53e5\u7528\u4e8e\u5220\u9664\u6570\u636e\u5e93\uff0c\u5305\u62ec\u5176\u4e2d\u7684\u6240\u6709\u8868\u3001\u89c6\u56fe\u3001\u5b58\u50a8\u8fc7\u7a0b\u7b49\u6570\u636e\u5e93\u5bf9\u8c61\u3002<\/p>\n<p>DROP DATABASE \u662f\u4e00\u4e2a\u975e\u5e38\u5f3a\u5927\u548c\u5371\u9669\u7684\u64cd\u4f5c\uff0c\u56e0\u4e3a\u5b83\u4f1a\u6c38\u4e45\u5220\u9664\u6574\u4e2a\u6570\u636e\u5e93\u53ca\u5176\u6240\u6709\u76f8\u5173\u6570\u636e\uff0c\u56e0\u6b64\u5728\u6267\u884c\u4e4b\u524d\u52a1\u5fc5\u8981\u614e\u91cd\u8003\u8651\u5e76\u786e\u4fdd\u4f60\u771f\u7684\u5e0c\u671b\u6267\u884c\u6b64\u64cd\u4f5c\u3002<\/p>\n<h3 id=\"\u8bed\u6cd5\u683c\u5f0f-3\">\u8bed\u6cd5\u683c\u5f0f\uff1a<\/h3>\n<pre><code class=\"language-mysql\" lang=\"mysql\">DROP DATABASE [IF EXISTS] database_name;\n<\/code><\/pre>\n<p><strong>\u53c2\u6570\u8bf4\u660e\uff1a<\/strong><\/p>\n<ul>\n<li><code>DROP DATABASE<\/code>\uff1a\u8868\u793a\u5220\u9664\u6570\u636e\u5e93\u7684\u64cd\u4f5c\u3002<\/li>\n<li><code>IF EXISTS<\/code>\uff1a\u662f\u4e00\u4e2a\u53ef\u9009\u7684\u5b50\u53e5\uff0c\u7528\u4e8e\u68c0\u67e5\u6570\u636e\u5e93\u662f\u5426\u5b58\u5728\u3002\u5982\u679c\u5b58\u5728\uff0c\u6267\u884c\u5220\u9664\u64cd\u4f5c\uff1b\u5982\u679c\u4e0d\u5b58\u5728\uff0c\u4e0d\u4f1a\u62a5\u9519\u3002<\/li>\n<li><code>database_name<\/code>\uff1a\u8981\u5220\u9664\u7684\u6570\u636e\u5e93\u7684\u540d\u79f0\u3002<\/li>\n<\/ul>\n<p>\u4ee5\u4e0b\u662f\u4e00\u4e2a\u7b80\u5355\u7684\u4f8b\u5b50\uff0c\u5047\u8bbe\u8981\u5220\u9664\u540d\u4e3a my_database \u7684\u6570\u636e\u5e93\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">DROP DATABASE IF EXISTS my_database;\n<\/code><\/pre>\n<p>\u5728\u6267\u884c <strong>DROP DATABASE<\/strong> \u4e4b\u524d\uff0c\u8bf7\u786e\u4fdd\u4f60\u5df2\u7ecf\u5907\u4efd\u4e86\u6570\u636e\u5e93\u4e2d\u7684\u91cd\u8981\u6570\u636e\uff0c\u5e76\u4e14\u4f60\u786e\u5b9e\u6709\u6743\u9650\u6267\u884c\u8fd9\u4e2a\u64cd\u4f5c\uff0c\u56e0\u4e3a\u5220\u9664\u6570\u636e\u5e93\u901a\u5e38\u9700\u8981\u7ba1\u7406\u5458\u6216\u8d85\u7ea7\u7528\u6237\u7684\u6743\u9650\u3002\u6b64\u5916\uff0c\u6267\u884c\u6b64\u7c7b\u64cd\u4f5c\u4e4b\u524d\u6700\u597d\u5148\u786e\u8ba4\u6ca1\u6709\u5176\u4ed6\u7528\u6237\u6b63\u5728\u4f7f\u7528\u8be5\u6570\u636e\u5e93\u3002<\/p>\n<h3 id=\"truncate-table-\u8bed\u53e5\">TRUNCATE TABLE \u8bed\u53e5<\/h3>\n<p>\u5982\u679c\u6211\u4eec\u4ec5\u4ec5\u9700\u8981\u5220\u9664\u8868\u5185\u7684\u6570\u636e\uff0c\u4f46\u5e76\u4e0d\u5220\u9664\u8868\u672c\u8eab\uff0c\u90a3\u4e48\u6211\u4eec\u8be5\u5982\u4f55\u505a\u5462\uff1f<\/p>\n<p>\u5728 SQL \u4e2d\uff0cTRUNCATE TABLE\u8bed\u53e5\u7528\u4e8e\u5feb\u901f\u5220\u9664\u8868\u4e2d\u7684\u6240\u6709\u6570\u636e\uff0c\u4f46\u4fdd\u7559\u8868\u7684\u7ed3\u6784\uff08\u5217\u3001\u7ea6\u675f\u7b49\uff09\uff0c\u4e0e DELETE \u8bed\u53e5\u76f8\u6bd4\uff0cTRUNCATE TABLE \u901a\u5e38\u66f4\u5feb\uff0c\u56e0\u4e3a\u5b83\u662f\u901a\u8fc7\u5220\u9664\u8868\u4e2d\u7684\u6240\u6709\u884c\u800c\u4e0d\u662f\u9010\u884c\u5220\u9664\u5b9e\u73b0\u7684\u3002<\/p>\n<p>\u7136\u800c\uff0c\u9700\u8981\u6ce8\u610f\u7684\u662f\uff0cTRUNCATE TABLE\u4e0d\u4f1a\u89e6\u53d1\u89e6\u53d1\u5668\uff0c\u800c\u4e14\u65e0\u6cd5\u5728\u4e8b\u52a1\u4e2d\u8fdb\u884c\u56de\u6eda\u3002<\/p>\n<p>\u8bf7\u4f7f\u7528 TRUNCATE TABLE \u8bed\u53e5\uff1a<\/p>\n<h3 id=\"\u8bed\u6cd5\u683c\u5f0f-4\">\u8bed\u6cd5\u683c\u5f0f\uff1a<\/h3>\n<pre><code class=\"language-mysql\" lang=\"mysql\">TRUNCATE TABLE TABLE_NAME;\n<\/code><\/pre>\n<p><strong>\u53c2\u6570\u8bf4\u660e\uff1a<\/strong><\/p>\n<ul>\n<li><code>TRUNCATE TABLE<\/code>\uff1a\u8868\u793a\u6e05\u7a7a\u8868\u7684\u64cd\u4f5c\u3002<\/li>\n<li><code>table_name<\/code>\uff1a\u8981\u6e05\u7a7a\u7684\u8868\u7684\u540d\u79f0\u3002<\/li>\n<\/ul>\n<p>\u4ee5\u4e0b\u662f\u4e00\u4e2a\u7b80\u5355\u7684\u4f8b\u5b50\uff0c\u5047\u8bbe\u8981\u6e05\u7a7a\u540d\u4e3a my_table \u7684\u8868\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">TRUNCATE TABLE my_table;\n<\/code><\/pre>\n<p>\u5f53\u4f7f\u7528 TRUNCATE TABLE \u6e05\u9664\u6570\u636e\u65f6\uff0c\u8868\u7684\u4e3b\u952e\u81ea\u589e\u503c\u5c06\u88ab\u91cd\u7f6e\u4e3a\u9ed8\u8ba4\u7684\u8d77\u59cb\u503c\uff0c\u901a\u5e38\u662f\u4ece 1 \u5f00\u59cb\u3002\u8fd9\u610f\u5473\u7740\u4e0b\u4e00\u6b21\u63d2\u5165\u6570\u636e\u65f6\uff0c\u4e3b\u952e\u5c06\u4ece 1 \u5f00\u59cb\u9012\u589e\u3002\u4e0e\u4e4b\u4e0d\u540c\u7684\u662f\uff0c\u4f7f\u7528 DELETE \u8bed\u53e5\u5220\u9664\u6570\u636e\u5e76\u4e0d\u4f1a\u91cd\u7f6e\u4e3b\u952e\u81ea\u589e\u503c\uff0c\u800c\u662f\u4fdd\u7559\u5f53\u524d\u7684\u81ea\u589e\u503c\u3002<\/p>\n<hr \/>\n<h2 id=\"alter-table-\u8bed\u53e5\">ALTER TABLE \u8bed\u53e5<\/h2>\n<p>ALTER TABLE \u8bed\u53e5\u7528\u4e8e\u5728\u5df2\u6709\u7684\u8868\u4e2d\u6dfb\u52a0\u3001\u5220\u9664\u6216\u4fee\u6539\u5217\u3002<\/p>\n<h3 id=\"sql-alter-table-\u8bed\u6cd5\">SQL ALTER TABLE \u8bed\u6cd5<\/h3>\n<p>\u5982\u9700\u5728\u8868\u4e2d\u6dfb\u52a0\u5217\uff0c\u8bf7\u4f7f\u7528\u4e0b\u9762\u7684\u8bed\u6cd5:<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">ALTER TABLE table_name\nADD column_name datatype\n<\/code><\/pre>\n<p>\u5982\u9700\u5220\u9664\u8868\u4e2d\u7684\u5217\uff0c\u8bf7\u4f7f\u7528\u4e0b\u9762\u7684\u8bed\u6cd5\uff08\u8bf7\u6ce8\u610f\uff0c\u67d0\u4e9b\u6570\u636e\u5e93\u7cfb\u7edf\u4e0d\u5141\u8bb8\u8fd9\u79cd\u5728\u6570\u636e\u5e93\u8868\u4e2d\u5220\u9664\u5217\u7684\u65b9\u5f0f\uff09\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">ALTER TABLE table_name\nDROP COLUMN column_name\n<\/code><\/pre>\n<p>\u8981\u6539\u53d8\u8868\u4e2d\u5217\u7684\u6570\u636e\u7c7b\u578b\uff0c\u8bf7\u4f7f\u7528\u4e0b\u9762\u7684\u8bed\u6cd5\uff1a<\/p>\n<p><strong>My SQL \/ Oracle\uff1a<\/strong><\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">ALTER TABLE table_name\nMODIFY COLUMN column_name datatype\n<\/code><\/pre>\n<h3 id=\"sql-alter-table-\u5b9e\u4f8b\">SQL ALTER TABLE \u5b9e\u4f8b<\/h3>\n<p>\u8bf7\u770b &#8220;Persons&#8221; \u8868\uff1a<\/p>\n<figure class=\"table-figure\">\n<table>\n<thead>\n<tr>\n<th style=\"text-align: left;\">P_Id<\/th>\n<th style=\"text-align: left;\">LastName<\/th>\n<th style=\"text-align: left;\">FirstName<\/th>\n<th style=\"text-align: left;\">Address<\/th>\n<th style=\"text-align: left;\">City<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td style=\"text-align: left;\">1<\/td>\n<td style=\"text-align: left;\">Hansen<\/td>\n<td style=\"text-align: left;\">Ola<\/td>\n<td style=\"text-align: left;\">Timoteivn 10<\/td>\n<td style=\"text-align: left;\">Sandnes<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">2<\/td>\n<td style=\"text-align: left;\">Svendson<\/td>\n<td style=\"text-align: left;\">Tove<\/td>\n<td style=\"text-align: left;\">Borgvn 23<\/td>\n<td style=\"text-align: left;\">Sandnes<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">3<\/td>\n<td style=\"text-align: left;\">Pettersen<\/td>\n<td style=\"text-align: left;\">Kari<\/td>\n<td style=\"text-align: left;\">Storgt 20<\/td>\n<td style=\"text-align: left;\">Stavanger<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<p>\u73b0\u5728\uff0c\u6211\u4eec\u60f3\u5728 &#8220;Persons&#8221; \u8868\u4e2d\u6dfb\u52a0\u4e00\u4e2a\u540d\u4e3a &#8220;DateOfBirth&#8221; \u7684\u5217\u3002<\/p>\n<p>\u6211\u4eec\u4f7f\u7528\u4e0b\u9762\u7684 SQL \u8bed\u53e5\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">ALTER TABLE Persons\nADD DateOfBirth date\n<\/code><\/pre>\n<p>\u73b0\u5728\uff0c&#8221;Persons&#8221; \u8868\u5c06\u5982\u4e0b\u6240\u793a\uff1a<\/p>\n<figure class=\"table-figure\">\n<table>\n<thead>\n<tr>\n<th style=\"text-align: left;\">P_Id<\/th>\n<th style=\"text-align: left;\">LastName<\/th>\n<th style=\"text-align: left;\">FirstName<\/th>\n<th style=\"text-align: left;\">Address<\/th>\n<th style=\"text-align: left;\">City<\/th>\n<th style=\"text-align: left;\">DateOfBirth<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td style=\"text-align: left;\">1<\/td>\n<td style=\"text-align: left;\">Hansen<\/td>\n<td style=\"text-align: left;\">Ola<\/td>\n<td style=\"text-align: left;\">Timoteivn 10<\/td>\n<td style=\"text-align: left;\">Sandnes<\/td>\n<td style=\"text-align: left;\"><\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">2<\/td>\n<td style=\"text-align: left;\">Svendson<\/td>\n<td style=\"text-align: left;\">Tove<\/td>\n<td style=\"text-align: left;\">Borgvn 23<\/td>\n<td style=\"text-align: left;\">Sandnes<\/td>\n<td style=\"text-align: left;\"><\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">3<\/td>\n<td style=\"text-align: left;\">Pettersen<\/td>\n<td style=\"text-align: left;\">Kari<\/td>\n<td style=\"text-align: left;\">Storgt 20<\/td>\n<td style=\"text-align: left;\">Stavanger<\/td>\n<td style=\"text-align: left;\"><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<h3 id=\"\u6539\u53d8\u6570\u636e\u7c7b\u578b\u5b9e\u4f8b\">\u6539\u53d8\u6570\u636e\u7c7b\u578b\u5b9e\u4f8b<\/h3>\n<p>\u73b0\u5728\uff0c\u6211\u4eec\u60f3\u8981\u6539\u53d8 &#8220;Persons&#8221; \u8868\u4e2d &#8220;DateOfBirth&#8221; \u5217\u7684\u6570\u636e\u7c7b\u578b\u3002<\/p>\n<p>\u6211\u4eec\u4f7f\u7528\u4e0b\u9762\u7684 SQL \u8bed\u53e5\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">ALTER TABLE Persons\nALTER COLUMN DateOfBirth year\n<\/code><\/pre>\n<p>\u8bf7\u6ce8\u610f\uff0c\u73b0\u5728 &#8220;DateOfBirth&#8221; \u5217\u7684\u7c7b\u578b\u662f year\uff0c\u53ef\u4ee5\u5b58\u653e 2 \u4f4d\u6216 4 \u4f4d\u683c\u5f0f\u7684\u5e74\u4efd\u3002<\/p>\n<h3 id=\"drop-column-\u5b9e\u4f8b\">DROP COLUMN \u5b9e\u4f8b<\/h3>\n<p>\u63a5\u4e0b\u6765\uff0c\u6211\u4eec\u60f3\u8981\u5220\u9664 &#8220;Person&#8221; \u8868\u4e2d\u7684 &#8220;DateOfBirth&#8221; \u5217\u3002<\/p>\n<p>\u6211\u4eec\u4f7f\u7528\u4e0b\u9762\u7684 SQL \u8bed\u53e5\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">ALTER TABLE Persons\nDROP COLUMN DateOfBirth\n<\/code><\/pre>\n<p>\u73b0\u5728\uff0c&#8221;Persons&#8221; \u8868\u5c06\u5982\u4e0b\u6240\u793a\uff1a<\/p>\n<figure class=\"table-figure\">\n<table>\n<thead>\n<tr>\n<th style=\"text-align: left;\">P_Id<\/th>\n<th style=\"text-align: left;\">LastName<\/th>\n<th style=\"text-align: left;\">FirstName<\/th>\n<th style=\"text-align: left;\">Address<\/th>\n<th style=\"text-align: left;\">City<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td style=\"text-align: left;\">1<\/td>\n<td style=\"text-align: left;\">Hansen<\/td>\n<td style=\"text-align: left;\">Ola<\/td>\n<td style=\"text-align: left;\">Timoteivn 10<\/td>\n<td style=\"text-align: left;\">Sandnes<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">2<\/td>\n<td style=\"text-align: left;\">Svendson<\/td>\n<td style=\"text-align: left;\">Tove<\/td>\n<td style=\"text-align: left;\">Borgvn 23<\/td>\n<td style=\"text-align: left;\">Sandnes<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">3<\/td>\n<td style=\"text-align: left;\">Pettersen<\/td>\n<td style=\"text-align: left;\">Kari<\/td>\n<td style=\"text-align: left;\">Storgt 20<\/td>\n<td style=\"text-align: left;\">Stavanger<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<hr \/>\n<h2 id=\"auto-increment-\u5b57\u6bb5\">AUTO INCREMENT \u5b57\u6bb5<\/h2>\n<p>\u6211\u4eec\u901a\u5e38\u5e0c\u671b\u5728\u6bcf\u6b21\u63d2\u5165\u65b0\u8bb0\u5f55\u65f6\uff0c\u81ea\u52a8\u5730\u521b\u5efa\u4e3b\u952e\u5b57\u6bb5\u7684\u503c\u3002<\/p>\n<p>\u6211\u4eec\u53ef\u4ee5\u5728\u8868\u4e2d\u521b\u5efa\u4e00\u4e2a auto-increment \u5b57\u6bb5\u3002<\/p>\n<hr \/>\n<h2 id=\"\u7528\u4e8e-mysql-\u7684\u8bed\u6cd5\">\u7528\u4e8e MySQL \u7684\u8bed\u6cd5<\/h2>\n<p>\u4e0b\u9762\u7684 SQL \u8bed\u53e5\u628a &#8220;Persons&#8221; \u8868\u4e2d\u7684 &#8220;ID&#8221; \u5217\u5b9a\u4e49\u4e3a auto-increment \u4e3b\u952e\u5b57\u6bb5\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">CREATE TABLE Persons\n(\nID int NOT NULL AUTO_INCREMENT,\nLastName varchar(255) NOT NULL,\nFirstName varchar(255),\nAddress varchar(255),\nCity varchar(255),\nPRIMARY KEY (ID)\n)\n<\/code><\/pre>\n<p>MySQL \u4f7f\u7528 AUTO_INCREMENT \u5173\u952e\u5b57\u6765\u6267\u884c auto-increment \u4efb\u52a1\u3002<\/p>\n<p>\u9ed8\u8ba4\u5730\uff0cAUTO_INCREMENT \u7684\u5f00\u59cb\u503c\u662f 1\uff0c\u6bcf\u6761\u65b0\u8bb0\u5f55\u9012\u589e 1\u3002<\/p>\n<p>\u8981\u8ba9 AUTO_INCREMENT \u5e8f\u5217\u4ee5\u5176\u4ed6\u7684\u503c\u8d77\u59cb\uff0c\u8bf7\u4f7f\u7528\u4e0b\u9762\u7684 SQL \u8bed\u6cd5\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">ALTER TABLE Persons AUTO_INCREMENT=100\n<\/code><\/pre>\n<p>\u8981\u5728 &#8220;Persons&#8221; \u8868\u4e2d\u63d2\u5165\u65b0\u8bb0\u5f55\uff0c\u6211\u4eec\u4e0d\u5fc5\u4e3a &#8220;ID&#8221; \u5217\u89c4\u5b9a\u503c\uff08\u4f1a\u81ea\u52a8\u6dfb\u52a0\u4e00\u4e2a\u552f\u4e00\u7684\u503c\uff09\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">INSERT INTO Persons (FirstName,LastName)\nVALUES ('Lars','Monsen')\n<\/code><\/pre>\n<p>\u4e0a\u9762\u7684 SQL \u8bed\u53e5\u4f1a\u5728 &#8220;Persons&#8221; \u8868\u4e2d\u63d2\u5165\u4e00\u6761\u65b0\u8bb0\u5f55\u3002&#8221;ID&#8221; \u5217\u4f1a\u88ab\u8d4b\u4e88\u4e00\u4e2a\u552f\u4e00\u7684\u503c\u3002&#8221;FirstName&#8221; \u5217\u4f1a\u88ab\u8bbe\u7f6e\u4e3a &#8220;Lars&#8221;\uff0c&#8221;LastName&#8221; \u5217\u4f1a\u88ab\u8bbe\u7f6e\u4e3a &#8220;Monsen&#8221;\u3002<\/p>\n<hr \/>\n<h2 id=\"sql-create-view-\u8bed\u53e5\">SQL CREATE VIEW \u8bed\u53e5<\/h2>\n<p>\u5728 SQL \u4e2d\uff0c\u89c6\u56fe\u662f\u57fa\u4e8e SQL \u8bed\u53e5\u7684\u7ed3\u679c\u96c6\u7684\u53ef\u89c6\u5316\u7684\u8868\u3002<\/p>\n<p>\u89c6\u56fe\u5305\u542b\u884c\u548c\u5217\uff0c\u5c31\u50cf\u4e00\u4e2a\u771f\u5b9e\u7684\u8868\u3002\u89c6\u56fe\u4e2d\u7684\u5b57\u6bb5\u5c31\u662f\u6765\u81ea\u4e00\u4e2a\u6216\u591a\u4e2a\u6570\u636e\u5e93\u4e2d\u7684\u771f\u5b9e\u7684\u8868\u4e2d\u7684\u5b57\u6bb5\u3002<\/p>\n<p>\u60a8\u53ef\u4ee5\u5411\u89c6\u56fe\u6dfb\u52a0 SQL \u51fd\u6570\u3001WHERE \u4ee5\u53ca JOIN \u8bed\u53e5\uff0c\u4e5f\u53ef\u4ee5\u5448\u73b0\u6570\u636e\uff0c\u5c31\u50cf\u8fd9\u4e9b\u6570\u636e\u6765\u81ea\u4e8e\u67d0\u4e2a\u5355\u4e00\u7684\u8868\u4e00\u6837\u3002<\/p>\n<h3 id=\"sql-create-view-\u8bed\u6cd5\">SQL CREATE VIEW \u8bed\u6cd5<\/h3>\n<pre><code class=\"language-mysql\" lang=\"mysql\">CREATE VIEW view_name AS\nSELECT column1, column2, ...\nFROM table_name\nWHERE condition;\n<\/code><\/pre>\n<p><strong>\u53c2\u6570\u8bf4\u660e\uff1a<\/strong><\/p>\n<ul>\n<li><strong>CREATE VIEW:<\/strong> \u58f0\u660e\u4f60\u8981\u521b\u5efa\u4e00\u4e2a\u89c6\u56fe\u3002<\/li>\n<li><strong>view_name:<\/strong> \u6307\u5b9a\u89c6\u56fe\u7684\u540d\u79f0\u3002<\/li>\n<li><strong>AS:<\/strong> \u6307\u5b9a\u5173\u952e\u5b57\uff0c\u8868\u793a\u89c6\u56fe\u7684\u5b9a\u4e49\u5f00\u59cb\u3002<\/li>\n<li><strong>SELECT column1, column2, &#8230;:<\/strong> \u6307\u5b9a\u89c6\u56fe\u4e2d\u5305\u542b\u7684\u5217\uff0c\u53ef\u4ee5\u662f\u8868\u4e2d\u7684\u5217\u6216\u8ba1\u7b97\u5217\u3002<\/li>\n<li><strong>FROM table_name:<\/strong> \u6307\u5b9a\u89c6\u56fe\u4ece\u54ea\u4e2a\u8868\u4e2d\u83b7\u53d6\u6570\u636e\u3002<\/li>\n<li><strong>WHERE condition:<\/strong> \u53ef\u9009\u90e8\u5206\uff0c\u7528\u4e8e\u6307\u5b9a\u7b5b\u9009\u6761\u4ef6\uff0c\u9650\u5236\u89c6\u56fe\u4e2d\u7684\u884c\u3002<\/li>\n<\/ul>\n<p><strong>\u6ce8\u91ca\uff1a<\/strong>\u89c6\u56fe\u603b\u662f\u663e\u793a\u6700\u65b0\u7684\u6570\u636e\uff01\u6bcf\u5f53\u7528\u6237\u67e5\u8be2\u89c6\u56fe\u65f6\uff0c\u6570\u636e\u5e93\u5f15\u64ce\u901a\u8fc7\u4f7f\u7528\u89c6\u56fe\u7684 SQL \u8bed\u53e5\u91cd\u5efa\u6570\u636e\u3002<\/p>\n<h3 id=\"sql-create-view-\u5b9e\u4f8b\">SQL CREATE VIEW \u5b9e\u4f8b<\/h3>\n<p>\u5047\u8bbe\u4f60\u6709\u4e00\u4e2a\u5305\u542b\u5458\u5de5\u4fe1\u606f\u7684\u8868 employees\uff0c\u5305\u62ec\u4ee5\u4e0b\u5217\uff1aemployee_id\u3001first_name\u3001last_name\u3001salary \u548c department_id\uff0c\u73b0\u5728\uff0c\u6211\u4eec\u5c06\u521b\u5efa\u4e00\u4e2a\u89c6\u56fe\uff0c\u663e\u793a\u5de5\u8d44\u9ad8\u4e8e\u67d0\u4e2a\u9608\u503c\u7684\u5458\u5de5\u4fe1\u606f\u3002<\/p>\n<p>\u5b9e\u4f8b\u5982\u4e0b\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">-- \u521b\u5efa\u5305\u542b\u9ad8\u5de5\u8d44\u5458\u5de5\u4fe1\u606f\u7684\u89c6\u56fe\nCREATE VIEW high_salary_employees AS\nSELECT employee_id, first_name, last_name, salary\nFROM employees\nWHERE salary &gt; 50000;\n<\/code><\/pre>\n<p>\u5728\u8fd9\u4e2a\u4f8b\u5b50\u4e2d\uff0c\u6211\u4eec\u521b\u5efa\u4e86\u4e00\u4e2a\u540d\u4e3a high_salary_employees \u7684\u89c6\u56fe\uff0c\u8be5\u89c6\u56fe\u5305\u542b\u4e86\u90a3\u4e9b\u5de5\u8d44\u9ad8\u4e8e 50000 \u7684\u5458\u5de5\u7684\u4fe1\u606f\u3002<\/p>\n<p>\u73b0\u5728\uff0c\u4f60\u53ef\u4ee5\u50cf\u67e5\u8be2\u666e\u901a\u8868\u4e00\u6837\u4f7f\u7528\u8fd9\u4e2a\u89c6\u56fe\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">-- \u67e5\u8be2\u9ad8\u5de5\u8d44\u5458\u5de5\u89c6\u56fe\nSELECT *\nFROM high_salary_employees;\n<\/code><\/pre>\n<p>\u8fd9\u5c06\u8fd4\u56de\u6240\u6709\u5de5\u8d44\u9ad8\u4e8e 50000 \u7684\u5458\u5de5\u7684\u8be6\u7ec6\u4fe1\u606f\uff0c\u800c\u4e0d\u9700\u8981\u6bcf\u6b21\u90fd\u7f16\u5199\u76f8\u540c\u7684\u7b5b\u9009\u6761\u4ef6\u3002<\/p>\n<p>\u503c\u5f97\u6ce8\u610f\u7684\u662f\uff0c\u89c6\u56fe\u672c\u8d28\u4e0a\u662f\u4e00\u4e2a\u865a\u62df\u7684\u8868\uff0c\u5b83\u5e76\u4e0d\u5b58\u50a8\u6570\u636e\uff0c\u800c\u662f\u57fa\u4e8e\u57fa\u7840\u8868\u7684\u67e5\u8be2\u7ed3\u679c\u751f\u6210\u3002\u56e0\u6b64\uff0c\u5982\u679c\u57fa\u7840\u8868\u7684\u6570\u636e\u53d1\u751f\u53d8\u5316\uff0c\u89c6\u56fe\u7684\u5185\u5bb9\u4e5f\u4f1a\u76f8\u5e94\u5730\u66f4\u65b0\u3002<\/p>\n<h3 id=\"sql-\u66f4\u65b0\u89c6\u56fe\">SQL \u66f4\u65b0\u89c6\u56fe<\/h3>\n<p>\u5728 SQL \u4e2d\uff0c\u4f60\u4e0d\u80fd\u76f4\u63a5\u4f7f\u7528 UPDATE \u8bed\u53e5\u6765\u66f4\u65b0\u89c6\u56fe\uff0c\u56e0\u4e3a\u89c6\u56fe\u662f\u57fa\u4e8e\u67e5\u8be2\u7ed3\u679c\u751f\u6210\u7684\u865a\u62df\u8868\uff0c\u800c\u4e0d\u662f\u5b9e\u9645\u5b58\u50a8\u6570\u636e\u7684\u8868\u3002<\/p>\n<p>\u66f4\u65b0\u89c6\u56fe\u7684\u5b9e\u8d28\u662f\u901a\u8fc7\u66f4\u65b0\u89c6\u56fe\u6240\u57fa\u4e8e\u7684\u8868\u4e2d\u7684\u6570\u636e\uff0c\u7136\u540e\u89c6\u56fe\u4f1a\u53cd\u6620\u8fd9\u4e9b\u53d8\u5316\u3002<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">UPDATE table_name\nSET column1 = value1, column2 = value2, ...\nWHERE condition;\n<\/code><\/pre>\n<p>\u5176\u4e2d\uff0ctable_name \u662f\u57fa\u7840\u8868\u7684\u540d\u79f0\uff0ccolumn1, column2, &#8230; \u662f\u8981\u66f4\u65b0\u7684\u5217\uff0cvalue1, value2, &#8230; \u662f\u65b0\u7684\u503c\uff0ccondition \u662f\u66f4\u65b0\u7684\u6761\u4ef6\u3002<\/p>\n<p>\u73b0\u5728\uff0c\u6211\u4eec\u5e0c\u671b\u5411 &#8220;Current Product List&#8221; \u89c6\u56fe\u6dfb\u52a0 &#8220;Category&#8221; \u5217\u3002\u6211\u4eec\u5c06\u901a\u8fc7\u4e0b\u5217 SQL \u66f4\u65b0\u89c6\u56fe\uff1a<\/p>\n<p>\u4e3e\u4f8b\u6765\u8bf4\uff0c\u5982\u679c\u4f60\u6709\u4e00\u4e2a\u540d\u4e3a high_salary_employees \u7684\u89c6\u56fe\uff0c\u663e\u793a\u5de5\u8d44\u9ad8\u4e8e 50000 \u7684\u5458\u5de5\u4fe1\u606f\uff0c\u800c\u8fd9\u4e2a\u89c6\u56fe\u57fa\u4e8e employees \u8868\u7684\u67e5\u8be2\u7ed3\u679c\uff0c\u4f60\u53ef\u4ee5\u901a\u8fc7\u4ee5\u4e0b\u6b65\u9aa4\u6765\u66f4\u65b0\u6570\u636e\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">-- \u6b65\u9aa4 1: \u66f4\u65b0 employees \u8868\u4e2d\u7684\u6570\u636e\nUPDATE employees\nSET salary = 60000\nWHERE employee_id = 1001;\n\n-- \u6b65\u9aa4 2: \u67e5\u8be2\u66f4\u65b0\u540e\u7684\u9ad8\u5de5\u8d44\u5458\u5de5\u89c6\u56fe\nSELECT *\nFROM high_salary_employees;\n<\/code><\/pre>\n<p>\u8fd9\u6837\uff0c\u4f60\u66f4\u65b0\u4e86 employees \u8868\u4e2d\u7684\u6570\u636e\uff0c\u800c\u89c6\u56fe high_salary_employees \u5c06\u53cd\u6620\u51fa\u8fd9\u4e9b\u53d8\u5316\u3002<\/p>\n<h3 id=\"sql-\u64a4\u9500\u89c6\u56fe\">SQL \u64a4\u9500\u89c6\u56fe<\/h3>\n<p>\u5728 SQL \u4e2d\uff0c\u64a4\u9500\uff08\u6216\u5220\u9664\uff09\u89c6\u56fe\u662f\u901a\u8fc7\u4f7f\u7528 DROP VIEW \u8bed\u53e5\u6765\u5b9e\u73b0\u7684\u3002<\/p>\n<p>DROP VIEW \u8bed\u53e5\u7528\u4e8e\u4ece\u6570\u636e\u5e93\u4e2d\u5220\u9664\u4e00\u4e2a\u5df2\u5b58\u5728\u7684\u89c6\u56fe\u3002\u8bed\u6cd5\u5982\u4e0b\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">DROP VIEW [IF EXISTS] view_name;\n<\/code><\/pre>\n<p><strong>\u53c2\u6570\u8bf4\u660e\uff1a<\/strong><\/p>\n<ul>\n<li><strong>DROP VIEW:<\/strong> \u8868\u793a\u4f60\u8981\u5220\u9664\u4e00\u4e2a\u89c6\u56fe\u3002<\/li>\n<li><strong>IF EXISTS:<\/strong> \u53ef\u9009\u90e8\u5206\uff0c\u7528\u4e8e\u68c0\u67e5\u89c6\u56fe\u662f\u5426\u5b58\u5728\u3002\u5982\u679c\u5b58\u5728\uff0c\u5219\u6267\u884c\u5220\u9664\u64cd\u4f5c\uff1b\u5982\u679c\u4e0d\u5b58\u5728\uff0c\u4e0d\u4f1a\u53d1\u751f\u9519\u8bef\u3002\u5728\u67d0\u4e9b\u6570\u636e\u5e93\u7cfb\u7edf\u4e2d\uff0c\u8fd9\u662f\u53ef\u9009\u7684\u3002<\/li>\n<li><strong>view_name:<\/strong> \u6307\u5b9a\u8981\u5220\u9664\u7684\u89c6\u56fe\u7684\u540d\u79f0\u3002<\/li>\n<\/ul>\n<p>\u5728\u6267\u884c\u4ee5\u4e0b\u8bed\u53e5\u540e\uff0c\u89c6\u56fe high_salary_employees \u5c06\u88ab\u4ece\u6570\u636e\u5e93\u4e2d\u5220\u9664\u3002<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">-- \u5220\u9664\u540d\u4e3a high_salary_employees \u7684\u89c6\u56fe\nDROP VIEW IF EXISTS high_salary_employees;\n<\/code><\/pre>\n<p>\u8bf7\u6ce8\u610f\uff0c\u8fd9\u5e76\u4e0d\u5f71\u54cd\u57fa\u7840\u8868\u4e2d\u7684\u6570\u636e\uff0c\u53ea\u662f\u5220\u9664\u4e86\u89c6\u56fe\u7684\u5b9a\u4e49\u3002<\/p>\n<p>\u5982\u679c\u4f60\u9700\u8981\u64a4\u9500\u6216\u5220\u9664\u67d0\u4e2a\u8868\u4e2d\u7684\u6570\u636e\uff0c\u5e94\u8be5\u4f7f\u7528 DROP TABLE \u8bed\u53e5\u3002<\/p>\n<p>\u5728\u4f7f\u7528 DROP VIEW \u8bed\u53e5\u65f6\uff0c\u8bf7\u786e\u4fdd\u4f60\u771f\u7684\u60f3\u8981\u5220\u9664\u8be5\u89c6\u56fe\uff0c\u56e0\u4e3a\u4e00\u65e6\u5220\u9664\uff0c\u5c06\u65e0\u6cd5\u6062\u590d\u89c6\u56fe\u7684\u5b9a\u4e49\u3002<\/p>\n<hr \/>\n<h2 id=\"sql-\u65e5\u671fdates\uff09\">SQL \u65e5\u671f\uff08Dates\uff09<\/h2>\n<p>\u5f53\u6211\u4eec\u5904\u7406\u65e5\u671f\u65f6\uff0c\u6700\u96be\u7684\u4efb\u52a1\u6050\u6015\u662f\u786e\u4fdd\u6240\u63d2\u5165\u7684\u65e5\u671f\u7684\u683c\u5f0f\uff0c\u4e0e\u6570\u636e\u5e93\u4e2d\u65e5\u671f\u5217\u7684\u683c\u5f0f\u76f8\u5339\u914d\u3002<\/p>\n<p>\u53ea\u8981\u60a8\u7684\u6570\u636e\u5305\u542b\u7684\u53ea\u662f\u65e5\u671f\u90e8\u5206\uff0c\u8fd0\u884c\u67e5\u8be2\u5c31\u4e0d\u4f1a\u51fa\u95ee\u9898\u3002\u4f46\u662f\uff0c\u5982\u679c\u6d89\u53ca\u65f6\u95f4\u90e8\u5206\uff0c\u60c5\u51b5\u5c31\u6709\u70b9\u590d\u6742\u4e86\u3002<\/p>\n<p>\u5728\u8ba8\u8bba\u65e5\u671f\u67e5\u8be2\u7684\u590d\u6742\u6027\u4e4b\u524d\uff0c\u6211\u4eec\u5148\u6765\u770b\u770b\u6700\u91cd\u8981\u7684\u5185\u5efa\u65e5\u671f\u5904\u7406\u51fd\u6570\u3002<\/p>\n<h3 id=\"mysql-date-\u51fd\u6570\">MySQL Date \u51fd\u6570<\/h3>\n<p>\u4e0b\u9762\u7684\u8868\u683c\u5217\u51fa\u4e86 MySQL \u4e2d\u6700\u91cd\u8981\u7684\u5185\u5efa\u65e5\u671f\u51fd\u6570\uff1a<\/p>\n<figure class=\"table-figure\">\n<table>\n<thead>\n<tr>\n<th style=\"text-align: left;\">\u51fd\u6570<\/th>\n<th style=\"text-align: left;\">\u63cf\u8ff0<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td style=\"text-align: left;\">NOW()<\/td>\n<td style=\"text-align: left;\">\u8fd4\u56de\u5f53\u524d\u7684\u65e5\u671f\u548c\u65f6\u95f4<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">CURDATE()<\/td>\n<td style=\"text-align: left;\">\u8fd4\u56de\u5f53\u524d\u7684\u65e5\u671f<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">CURTIME()<\/td>\n<td style=\"text-align: left;\">\u8fd4\u56de\u5f53\u524d\u7684\u65f6\u95f4<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">DATE()<\/td>\n<td style=\"text-align: left;\">\u63d0\u53d6\u65e5\u671f\u6216\u65e5\u671f\/\u65f6\u95f4\u8868\u8fbe\u5f0f\u7684\u65e5\u671f\u90e8\u5206<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">EXTRACT()<\/td>\n<td style=\"text-align: left;\">\u8fd4\u56de\u65e5\u671f\/\u65f6\u95f4\u7684\u5355\u72ec\u90e8\u5206<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">DATE_ADD()<\/td>\n<td style=\"text-align: left;\">\u5411\u65e5\u671f\u6dfb\u52a0\u6307\u5b9a\u7684\u65f6\u95f4\u95f4\u9694<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">DATE_SUB()<\/td>\n<td style=\"text-align: left;\">\u4ece\u65e5\u671f\u51cf\u53bb\u6307\u5b9a\u7684\u65f6\u95f4\u95f4\u9694<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">DATEDIFF()<\/td>\n<td style=\"text-align: left;\">\u8fd4\u56de\u4e24\u4e2a\u65e5\u671f\u4e4b\u95f4\u7684\u5929\u6570<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">DATE_FORMAT()<\/td>\n<td style=\"text-align: left;\">\u7528\u4e0d\u540c\u7684\u683c\u5f0f\u663e\u793a\u65e5\u671f\/\u65f6\u95f4<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<h3 id=\"sql-date-\u6570\u636e\u7c7b\u578b\">SQL Date \u6570\u636e\u7c7b\u578b<\/h3>\n<p><strong>MySQL<\/strong> \u4f7f\u7528\u4e0b\u5217\u6570\u636e\u7c7b\u578b\u5728\u6570\u636e\u5e93\u4e2d\u5b58\u50a8\u65e5\u671f\u6216\u65e5\u671f\/\u65f6\u95f4\u503c\uff1a<\/p>\n<ul>\n<li>DATE &#8211; \u683c\u5f0f\uff1aYYYY-MM-DD<\/li>\n<li>DATETIME &#8211; \u683c\u5f0f\uff1aYYYY-MM-DD HH:MM:SS<\/li>\n<li>TIMESTAMP &#8211; \u683c\u5f0f\uff1aYYYY-MM-DD HH:MM:SS<\/li>\n<li>YEAR &#8211; \u683c\u5f0f\uff1aYYYY \u6216 YY<\/li>\n<\/ul>\n<h2 id=\"sql-\u65e5\u671f\u5904\u7406\">SQL \u65e5\u671f\u5904\u7406<\/h2>\n<p>\u5982\u679c\u4e0d\u6d89\u53ca\u65f6\u95f4\u90e8\u5206\uff0c\u90a3\u4e48\u6211\u4eec\u53ef\u4ee5\u8f7b\u677e\u5730\u6bd4\u8f83\u4e24\u4e2a\u65e5\u671f\uff01<\/p>\n<p>\u5047\u8bbe\u6211\u4eec\u6709\u5982\u4e0b\u7684 &#8220;Orders&#8221; \u8868\uff1a<\/p>\n<figure class=\"table-figure\">\n<table>\n<thead>\n<tr>\n<th style=\"text-align: left;\">OrderId<\/th>\n<th style=\"text-align: left;\">ProductName<\/th>\n<th style=\"text-align: left;\">OrderDate<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td style=\"text-align: left;\">1<\/td>\n<td style=\"text-align: left;\">Geitost<\/td>\n<td style=\"text-align: left;\">2008-11-11<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">2<\/td>\n<td style=\"text-align: left;\">Camembert Pierrot<\/td>\n<td style=\"text-align: left;\">2008-11-09<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">3<\/td>\n<td style=\"text-align: left;\">Mozzarella di Giovanni<\/td>\n<td style=\"text-align: left;\">2008-11-11<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">4<\/td>\n<td style=\"text-align: left;\">Mascarpone Fabioli<\/td>\n<td style=\"text-align: left;\">2008-10-29<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<p>\u73b0\u5728\uff0c\u6211\u4eec\u5e0c\u671b\u4ece\u4e0a\u8868\u4e2d\u9009\u53d6 OrderDate \u4e3a &#8220;2008-11-11&#8221; \u7684\u8bb0\u5f55\u3002<\/p>\n<p>\u6211\u4eec\u4f7f\u7528\u4e0b\u9762\u7684 SELECT \u8bed\u53e5\uff1a<\/p>\n<p>SELECT * FROM Orders WHERE OrderDate=&#8217;2008-11-11&#8242;<\/p>\n<p>\u7ed3\u679c\u96c6\u5982\u4e0b\u6240\u793a\uff1a<\/p>\n<figure class=\"table-figure\">\n<table>\n<thead>\n<tr>\n<th style=\"text-align: left;\">OrderId<\/th>\n<th style=\"text-align: left;\">ProductName<\/th>\n<th style=\"text-align: left;\">OrderDate<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td style=\"text-align: left;\">1<\/td>\n<td style=\"text-align: left;\">Geitost<\/td>\n<td style=\"text-align: left;\">2008-11-11<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">3<\/td>\n<td style=\"text-align: left;\">Mozzarella di Giovanni<\/td>\n<td style=\"text-align: left;\">2008-11-11<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<p>\u73b0\u5728\uff0c\u5047\u8bbe &#8220;Orders&#8221; \u8868\u5982\u4e0b\u6240\u793a\uff08\u8bf7\u6ce8\u610f &#8220;OrderDate&#8221; \u5217\u4e2d\u7684\u65f6\u95f4\u90e8\u5206\uff09\uff1a<\/p>\n<figure class=\"table-figure\">\n<table>\n<thead>\n<tr>\n<th style=\"text-align: left;\">OrderId<\/th>\n<th style=\"text-align: left;\">ProductName<\/th>\n<th style=\"text-align: left;\">OrderDate<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td style=\"text-align: left;\">1<\/td>\n<td style=\"text-align: left;\">Geitost<\/td>\n<td style=\"text-align: left;\">2008-11-11 13:23:44<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">2<\/td>\n<td style=\"text-align: left;\">Camembert Pierrot<\/td>\n<td style=\"text-align: left;\">2008-11-09 15:45:21<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">3<\/td>\n<td style=\"text-align: left;\">Mozzarella di Giovanni<\/td>\n<td style=\"text-align: left;\">2008-11-11 11:12:01<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">4<\/td>\n<td style=\"text-align: left;\">Mascarpone Fabioli<\/td>\n<td style=\"text-align: left;\">2008-10-29 14:56:59<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<p>\u5982\u679c\u6211\u4eec\u4f7f\u7528\u548c\u4e0a\u9762\u4e00\u6837\u7684 SELECT \u8bed\u53e5\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT * FROM Orders WHERE OrderDate='2008-11-11'\n\n\u6216\n\nSELECT * FROM Orders WHERE OrderDate='2008-11-11 00\uff1a00\uff1a00'\n<\/code><\/pre>\n<p>\u90a3\u4e48\u6211\u4eec\u5c06\u5f97\u4e0d\u5230\u7ed3\u679c\uff01\u56e0\u4e3a\u8868\u4e2d\u6ca1\u6709&#8221;2008-11-11 00:00:00&#8243;\u65e5\u671f\u3002\u5982\u679c\u6ca1\u6709\u65f6\u95f4\u90e8\u5206\uff0c\u9ed8\u8ba4\u65f6\u95f4\u4e3a 00:00:00\u3002<\/p>\n<hr \/>\n<h2 id=\"sql-null-\u503c\">SQL NULL \u503c<\/h2>\n<p>\u5982\u679c\u8868\u4e2d\u7684\u67d0\u4e2a\u5217\u662f\u53ef\u9009\u7684\uff0c\u90a3\u4e48\u6211\u4eec\u53ef\u4ee5\u5728\u4e0d\u5411\u8be5\u5217\u6dfb\u52a0\u503c\u7684\u60c5\u51b5\u4e0b\u63d2\u5165\u65b0\u8bb0\u5f55\u6216\u66f4\u65b0\u5df2\u6709\u7684\u8bb0\u5f55\u3002\u8fd9\u610f\u5473\u7740\u8be5\u5b57\u6bb5\u5c06\u4ee5 NULL \u503c\u4fdd\u5b58\u3002<\/p>\n<p>NULL \u503c\u7684\u5904\u7406\u65b9\u5f0f\u4e0e\u5176\u4ed6\u503c\u4e0d\u540c\u3002<\/p>\n<p>NULL \u7528\u4f5c\u672a\u77e5\u7684\u6216\u4e0d\u9002\u7528\u7684\u503c\u7684\u5360\u4f4d\u7b26\u3002<\/p>\n<p><strong>\u6ce8\u91ca\uff1a<\/strong>\u65e0\u6cd5\u6bd4\u8f83 NULL \u548c 0\uff1b\u5b83\u4eec\u662f\u4e0d\u7b49\u4ef7\u7684\u3002<\/p>\n<hr \/>\n<h3 id=\"sql-\u7684-null-\u503c\u5904\u7406\">SQL \u7684 NULL \u503c\u5904\u7406<\/h3>\n<p>\u8bf7\u770b\u4e0b\u9762\u7684 &#8220;Persons&#8221; \u8868\uff1a<\/p>\n<figure class=\"table-figure\">\n<table>\n<thead>\n<tr>\n<th style=\"text-align: left;\">P_Id<\/th>\n<th style=\"text-align: left;\">LastName<\/th>\n<th style=\"text-align: left;\">FirstName<\/th>\n<th style=\"text-align: left;\">Address<\/th>\n<th style=\"text-align: left;\">City<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td style=\"text-align: left;\">1<\/td>\n<td style=\"text-align: left;\">Hansen<\/td>\n<td style=\"text-align: left;\">Ola<\/td>\n<td style=\"text-align: left;\"><\/td>\n<td style=\"text-align: left;\">Sandnes<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">2<\/td>\n<td style=\"text-align: left;\">Svendson<\/td>\n<td style=\"text-align: left;\">Tove<\/td>\n<td style=\"text-align: left;\">Borgvn 23<\/td>\n<td style=\"text-align: left;\">Sandnes<\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">3<\/td>\n<td style=\"text-align: left;\">Pettersen<\/td>\n<td style=\"text-align: left;\">Kari<\/td>\n<td style=\"text-align: left;\"><\/td>\n<td style=\"text-align: left;\">Stavanger<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<p>\u5047\u5982 &#8220;Persons&#8221; \u8868\u4e2d\u7684 &#8220;Address&#8221; \u5217\u662f\u53ef\u9009\u7684\u3002\u8fd9\u610f\u5473\u7740\u5982\u679c\u5728 &#8220;Address&#8221; \u5217\u63d2\u5165\u4e00\u6761\u4e0d\u5e26\u503c\u7684\u8bb0\u5f55\uff0c&#8221;Address&#8221; \u5217\u4f1a\u4f7f\u7528 NULL \u503c\u4fdd\u5b58\u3002<\/p>\n<p>\u90a3\u4e48\u6211\u4eec\u5982\u4f55\u6d4b\u8bd5 NULL \u503c\u5462\uff1f<\/p>\n<p>\u65e0\u6cd5\u4f7f\u7528\u6bd4\u8f83\u8fd0\u7b97\u7b26\u6765\u6d4b\u8bd5 NULL \u503c\uff0c\u6bd4\u5982 =\u3001&lt; \u6216 &lt;&gt;\u3002<\/p>\n<p>\u6211\u4eec\u5fc5\u987b\u4f7f\u7528 IS NULL \u548c IS NOT NULL \u64cd\u4f5c\u7b26\u3002<\/p>\n<h3 id=\"sql-is-null\">SQL IS NULL<\/h3>\n<p>\u6211\u4eec\u5982\u4f55\u4ec5\u4ec5\u9009\u53d6\u5728 &#8220;Address&#8221; \u5217\u4e2d\u5e26\u6709 NULL \u503c\u7684\u8bb0\u5f55\u5462\uff1f<\/p>\n<p>\u6211\u4eec\u5fc5\u987b\u4f7f\u7528 IS NULL \u64cd\u4f5c\u7b26\uff1a<\/p>\n<p>SELECT LastName,FirstName,Address FROM Persons<br \/>\nWHERE Address IS NULL<\/p>\n<p>\u7ed3\u679c\u96c6\u5982\u4e0b\u6240\u793a\uff1a<\/p>\n<figure class=\"table-figure\">\n<table>\n<thead>\n<tr>\n<th style=\"text-align: left;\">LastName<\/th>\n<th style=\"text-align: left;\">FirstName<\/th>\n<th style=\"text-align: left;\">Address<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td style=\"text-align: left;\">Hansen<\/td>\n<td style=\"text-align: left;\">Ola<\/td>\n<td style=\"text-align: left;\"><\/td>\n<\/tr>\n<tr>\n<td style=\"text-align: left;\">Pettersen<\/td>\n<td style=\"text-align: left;\">Kari<\/td>\n<td style=\"text-align: left;\"><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<p><strong>\u63d0\u793a\uff1a<\/strong>\u8bf7\u59cb\u7ec8\u4f7f\u7528 IS NULL \u6765\u67e5\u627e NULL \u503c\u3002<\/p>\n<h3 id=\"sql-is-not-null\">SQL IS NOT NULL<\/h3>\n<p>\u6211\u4eec\u5982\u4f55\u4ec5\u4ec5\u9009\u53d6\u5728 &#8220;Address&#8221; \u5217\u4e2d\u4e0d\u5e26\u6709 NULL \u503c\u7684\u8bb0\u5f55\u5462\uff1f<\/p>\n<p>\u6211\u4eec\u5fc5\u987b\u4f7f\u7528 IS NOT NULL \u64cd\u4f5c\u7b26\uff1a<\/p>\n<pre><code class=\"language-mysql\" lang=\"mysql\">SELECT LastName,FirstName,Address FROM Persons\nWHERE Address IS NOT NULL\n<\/code><\/pre>\n<p>\u7ed3\u679c\u96c6\u5982\u4e0b\u6240\u793a\uff1a<\/p>\n<figure class=\"table-figure\">\n<table>\n<thead>\n<tr>\n<th style=\"text-align: left;\">LastName<\/th>\n<th style=\"text-align: left;\">FirstName<\/th>\n<th style=\"text-align: left;\">Address<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td style=\"text-align: left;\">Svendson<\/td>\n<td style=\"text-align: left;\">Tove<\/td>\n<td style=\"text-align: left;\">Borgvn 23<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n","protected":false},"excerpt":{"rendered":"<p>SQL SELECT \u8bed\u53e5 SELECT \u8bed\u53e5\u7528\u4e8e\u4ece\u6570\u636e\u5e93\u4e2d\u9009\u53d6\u6570\u636e\u3002 \u7ed3\u679c\u88ab\u5b58\u50a8\u5728\u4e00\u4e2a\u7ed3\u679c\u8868\u4e2d\uff0c\u79f0\u4e3a\u7ed3\u679c\u96c6\u3002 [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17],"tags":[],"class_list":["post-271","post","type-post","status-publish","format-standard","hentry","category-17"],"_links":{"self":[{"href":"https:\/\/www.vanforever.com.cn\/index.php?rest_route=\/wp\/v2\/posts\/271","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.vanforever.com.cn\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.vanforever.com.cn\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.vanforever.com.cn\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.vanforever.com.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=271"}],"version-history":[{"count":2,"href":"https:\/\/www.vanforever.com.cn\/index.php?rest_route=\/wp\/v2\/posts\/271\/revisions"}],"predecessor-version":[{"id":273,"href":"https:\/\/www.vanforever.com.cn\/index.php?rest_route=\/wp\/v2\/posts\/271\/revisions\/273"}],"wp:attachment":[{"href":"https:\/\/www.vanforever.com.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=271"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.vanforever.com.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=271"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.vanforever.com.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=271"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}