{"id":77481,"date":"2024-10-16T10:49:40","date_gmt":"2024-10-16T02:49:40","guid":{"rendered":"https:\/\/server.hk\/cnblog\/77481\/"},"modified":"2024-10-16T10:49:40","modified_gmt":"2024-10-16T02:49:40","slug":"mysql%e8%aa%9e%e5%8f%a5%e4%b8%ad%e5%a6%82%e4%bd%95%e9%9d%88%e6%b4%bb%e5%b0%8dif%e4%be%8b%e5%ad%90%e9%80%b2%e8%a1%8c%e9%81%8b%e7%94%a8","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/77481\/","title":{"rendered":"MySQL\u8a9e\u53e5\u4e2d\u5982\u4f55\u9748\u6d3b\u5c0dif\u4f8b\u5b50\u9032\u884c\u904b\u7528"},"content":{"rendered":"<h1 id=\"mysql%e8%aa%9e%e5%8f%a5%e4%b8%ad%e5%a6%82%e4%bd%95%e9%9d%88%e6%b4%bb%e5%b0%8dif%e4%be%8b%e5%ad%90%e9%80%b2%e8%a1%8c%e9%81%8b%e7%94%a8-EGsxIbUTbR\">MySQL\u8a9e\u53e5\u4e2d\u5982\u4f55\u9748\u6d3b\u5c0dif\u4f8b\u5b50\u9032\u884c\u904b\u7528<\/h1>\n<p>\u5728\u6578\u64da\u5eab\u7ba1\u7406\u4e2d\uff0cMySQL\u662f\u4e00\u500b\u5ee3\u6cdb\u4f7f\u7528\u7684\u95dc\u4fc2\u578b\u6578\u64da\u5eab\u7cfb\u7d71\u3002\u5b83\u63d0\u4f9b\u4e86\u591a\u7a2e\u529f\u80fd\u4f86\u8655\u7406\u6578\u64da\uff0c\u5176\u4e2d\u4e4b\u4e00\u5c31\u662f\u689d\u4ef6\u8a9e\u53e5\u7684\u4f7f\u7528\u3002\u672c\u6587\u5c07\u63a2\u8a0e\u5982\u4f55\u5728MySQL\u8a9e\u53e5\u4e2d\u9748\u6d3b\u904b\u7528if\u8a9e\u53e5\uff0c\u4e26\u63d0\u4f9b\u4e00\u4e9b\u5be6\u969b\u7684\u4f8b\u5b50\u4f86\u5e6b\u52a9\u7406\u89e3\u3002<\/p>\n<h2 id=\"mysql%e4%b8%ad%e7%9a%84if%e8%aa%9e%e5%8f%a5%e6%a6%82%e8%bf%b0-EGsxIbUTbR\">MySQL\u4e2d\u7684IF\u8a9e\u53e5\u6982\u8ff0<\/h2>\n<p>\u5728MySQL\u4e2d\uff0cIF\u8a9e\u53e5\u662f\u4e00\u7a2e\u63a7\u5236\u6d41\u8a9e\u53e5\uff0c\u5141\u8a31\u6839\u64da\u7279\u5b9a\u689d\u4ef6\u57f7\u884c\u4e0d\u540c\u7684\u64cd\u4f5c\u3002\u9019\u4f7f\u5f97\u958b\u767c\u8005\u80fd\u5920\u6839\u64da\u6578\u64da\u7684\u72c0\u614b\u9032\u884c\u9748\u6d3b\u7684\u67e5\u8a62\u548c\u66f4\u65b0\u3002<\/p>\n<h3 id=\"if%e8%aa%9e%e5%8f%a5%e7%9a%84%e5%9f%ba%e6%9c%ac%e8%aa%9e%e6%b3%95-EGsxIbUTbR\">IF\u8a9e\u53e5\u7684\u57fa\u672c\u8a9e\u6cd5<\/h3>\n<pre><code>IF(condition, true_value, false_value)<\/code><\/pre>\n<p>\u5728\u9019\u88e1\uff0c<code>condition<\/code>\u662f\u8981\u6aa2\u67e5\u7684\u689d\u4ef6\uff0c<code>true_value<\/code>\u662f\u5728\u689d\u4ef6\u70ba\u771f\u6642\u8fd4\u56de\u7684\u503c\uff0c\u800c<code>false_value<\/code>\u5247\u662f\u5728\u689d\u4ef6\u70ba\u5047\u6642\u8fd4\u56de\u7684\u503c\u3002<\/p>\n<h2 id=\"%e4%bd%bf%e7%94%a8if%e8%aa%9e%e5%8f%a5%e7%9a%84%e5%af%a6%e9%9a%9b%e4%be%8b%e5%ad%90-EGsxIbUTbR\">\u4f7f\u7528IF\u8a9e\u53e5\u7684\u5be6\u969b\u4f8b\u5b50<\/h2>\n<h3 id=\"%e4%be%8b%e5%ad%901%ef%bc%9a%e8%a8%88%e7%ae%97%e6%8a%98%e6%89%a3-EGsxIbUTbR\">\u4f8b\u5b501\uff1a\u8a08\u7b97\u6298\u6263<\/h3>\n<p>\u5047\u8a2d\u6211\u5011\u6709\u4e00\u500b\u540d\u70ba<code>orders<\/code>\u7684\u8868\u683c\uff0c\u5176\u4e2d\u5305\u542b\u8a02\u55ae\u7684\u91d1\u984d\u3002\u6211\u5011\u5e0c\u671b\u6839\u64da\u8a02\u55ae\u91d1\u984d\u8a08\u7b97\u6298\u6263\u3002\u4ee5\u4e0b\u662f\u4f7f\u7528IF\u8a9e\u53e5\u7684\u67e5\u8a62\u793a\u4f8b\uff1a<\/p>\n<pre><code>SELECT order_id, amount,\n       IF(amount &gt; 1000, amount * 0.1, 0) AS discount\nFROM orders;<\/code><\/pre>\n<p>\u5728\u9019\u500b\u67e5\u8a62\u4e2d\uff0c\u7576\u8a02\u55ae\u91d1\u984d\u5927\u65bc1000\u6642\uff0c\u5c07\u8a08\u7b9710%\u7684\u6298\u6263\uff1b\u5426\u5247\uff0c\u6298\u6263\u70ba0\u3002<\/p>\n<h3 id=\"%e4%be%8b%e5%ad%902%ef%bc%9a%e6%a0%b9%e6%93%9a%e7%94%a8%e6%88%b6%e8%a7%92%e8%89%b2%e9%a1%af%e7%a4%ba%e4%b8%8d%e5%90%8c%e4%bf%a1%e6%81%af-EGsxIbUTbR\">\u4f8b\u5b502\uff1a\u6839\u64da\u7528\u6236\u89d2\u8272\u986f\u793a\u4e0d\u540c\u4fe1\u606f<\/h3>\n<p>\u5728\u4e00\u500b\u7528\u6236\u7ba1\u7406\u7cfb\u7d71\u4e2d\uff0c\u6211\u5011\u53ef\u80fd\u9700\u8981\u6839\u64da\u7528\u6236\u7684\u89d2\u8272\u986f\u793a\u4e0d\u540c\u7684\u4fe1\u606f\u3002\u4ee5\u4e0b\u662f\u5982\u4f55\u4f7f\u7528IF\u8a9e\u53e5\u4f86\u5be6\u73fe\u9019\u4e00\u9ede\uff1a<\/p>\n<pre><code>SELECT user_id, username, role,\n       IF(role = 'admin', '\u7ba1\u7406\u54e1', '\u666e\u901a\u7528\u6236') AS user_type\nFROM users;<\/code><\/pre>\n<p>\u9019\u500b\u67e5\u8a62\u5c07\u6839\u64da\u7528\u6236\u7684\u89d2\u8272\u8fd4\u56de\u201c\u7ba1\u7406\u54e1\u201d\u6216\u201c\u666e\u901a\u7528\u6236\u201d\u3002<\/p>\n<h2 id=\"if%e8%aa%9e%e5%8f%a5%e7%9a%84%e9%80%b2%e9%9a%8e%e7%94%a8%e6%b3%95-EGsxIbUTbR\">IF\u8a9e\u53e5\u7684\u9032\u968e\u7528\u6cd5<\/h2>\n<p>\u9664\u4e86\u57fa\u672c\u7684IF\u8a9e\u53e5\uff0cMySQL\u9084\u652f\u6301\u5d4c\u5957IF\u8a9e\u53e5\uff0c\u9019\u4f7f\u5f97\u6211\u5011\u53ef\u4ee5\u8655\u7406\u66f4\u8907\u96dc\u7684\u908f\u8f2f\u3002\u4f8b\u5982\uff1a<\/p>\n<pre><code>SELECT order_id, amount,\n       IF(amount &gt; 1000, '\u9ad8\u50f9\u8a02\u55ae',\n          IF(amount &gt; 500, '\u4e2d\u50f9\u8a02\u55ae', '\u4f4e\u50f9\u8a02\u55ae')) AS order_category\nFROM orders;<\/code><\/pre>\n<p>\u5728\u9019\u500b\u67e5\u8a62\u4e2d\uff0c\u6211\u5011\u6839\u64da\u8a02\u55ae\u91d1\u984d\u5c07\u8a02\u55ae\u5206\u985e\u70ba\u201c\u9ad8\u50f9\u8a02\u55ae\u201d\u3001\u201c\u4e2d\u50f9\u8a02\u55ae\u201d\u6216\u201c\u4f4e\u50f9\u8a02\u55ae\u201d\u3002<\/p>\n<h2 id=\"%e7%b5%90%e8%ab%96-EGsxIbUTbR\">\u7d50\u8ad6<\/h2>\n<p>MySQL\u4e2d\u7684IF\u8a9e\u53e5\u662f\u4e00\u500b\u5f37\u5927\u7684\u5de5\u5177\uff0c\u53ef\u4ee5\u5e6b\u52a9\u958b\u767c\u8005\u6839\u64da\u4e0d\u540c\u7684\u689d\u4ef6\u9748\u6d3b\u5730\u8655\u7406\u6578\u64da\u3002\u901a\u904e\u4e0a\u8ff0\u4f8b\u5b50\uff0c\u6211\u5011\u53ef\u4ee5\u770b\u5230IF\u8a9e\u53e5\u5728\u5be6\u969b\u61c9\u7528\u4e2d\u7684\u591a\u6a23\u6027\u548c\u9748\u6d3b\u6027\u3002\u7121\u8ad6\u662f\u5728\u8a08\u7b97\u6298\u6263\u9084\u662f\u6839\u64da\u7528\u6236\u89d2\u8272\u986f\u793a\u4fe1\u606f\uff0cIF\u8a9e\u53e5\u90fd\u80fd\u63d0\u4f9b\u6709\u6548\u7684\u89e3\u6c7a\u65b9\u6848\u3002<\/p>\n<p>\u5982\u679c\u60a8\u6b63\u5728\u5c0b\u627e\u9ad8\u6548\u7684\u6578\u64da\u5eab\u89e3\u6c7a\u65b9\u6848\uff0c\u8003\u616e\u4f7f\u7528<a href=\"https:\/\/server.hk\">\u9999\u6e2fVPS<\/a>\u4f86\u6258\u7ba1\u60a8\u7684MySQL\u6578\u64da\u5eab\uff0c\u9019\u5c07\u70ba\u60a8\u7684\u61c9\u7528\u63d0\u4f9b\u7a69\u5b9a\u548c\u5feb\u901f\u7684\u6027\u80fd\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u63a2\u7d22MySQL\u8a9e\u53e5\u4e2d\u9748\u6d3b\u904b\u7528IF\u7684\u6280\u5de7\uff0c\u901a\u904e\u5be6\u4f8b\u5b78\u7fd2\u5982\u4f55\u5728\u67e5\u8a62\u4e2d\u5be6\u73fe\u689d\u4ef6\u908f\u8f2f\u3002<\/p>\n","protected":false},"author":0,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[101],"tags":[],"class_list":["post-77481","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/77481","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/types\/post"}],"replies":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/comments?post=77481"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/77481\/revisions"}],"predecessor-version":[{"id":77488,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/77481\/revisions\/77488"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=77481"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=77481"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=77481"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}