{"id":76868,"date":"2024-10-16T10:06:14","date_gmt":"2024-10-16T02:06:14","guid":{"rendered":"https:\/\/server.hk\/cnblog\/76868\/"},"modified":"2024-10-16T10:06:14","modified_gmt":"2024-10-16T02:06:14","slug":"mysql%e6%a2%9d%e4%bb%b6select-case%e7%9a%84%e5%af%a6%e7%8f%be","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/76868\/","title":{"rendered":"MySQL\u689d\u4ef6select case\u7684\u5be6\u73fe"},"content":{"rendered":"<h1 id=\"mysql%e6%a2%9d%e4%bb%b6select-case%e7%9a%84%e5%af%a6%e7%8f%be-WaPBWFiBxu\">MySQL\u689d\u4ef6select case\u7684\u5be6\u73fe<\/h1>\n<p>\u5728\u6578\u64da\u5eab\u7ba1\u7406\u7cfb\u7d71\u4e2d\uff0cMySQL\u662f\u4e00\u500b\u5ee3\u6cdb\u4f7f\u7528\u7684\u958b\u6e90\u95dc\u806f\u6578\u64da\u5eab\u3002\u5b83\u63d0\u4f9b\u4e86\u591a\u7a2e\u529f\u80fd\u4f86\u8655\u7406\u548c\u67e5\u8a62\u6578\u64da\uff0c\u5176\u4e2d\u4e4b\u4e00\u5c31\u662f\u4f7f\u7528CASE\u8a9e\u53e5\u4f86\u5be6\u73fe\u689d\u4ef6\u9078\u64c7\u3002\u9019\u7bc7\u6587\u7ae0\u5c07\u6df1\u5165\u63a2\u8a0eMySQL\u4e2d\u7684CASE\u8a9e\u53e5\uff0c\u4e26\u63d0\u4f9b\u5be6\u969b\u7684\u793a\u4f8b\u4f86\u5e6b\u52a9\u8b80\u8005\u7406\u89e3\u5176\u7528\u6cd5\u3002<\/p>\n<h2 id=\"%e4%bb%80%e9%ba%bc%e6%98%afcase%e8%aa%9e%e5%8f%a5%ef%bc%9f-WaPBWFiBxu\">\u4ec0\u9ebc\u662fCASE\u8a9e\u53e5\uff1f<\/h2>\n<p>CASE\u8a9e\u53e5\u662f\u4e00\u7a2e\u689d\u4ef6\u8868\u9054\u5f0f\uff0c\u5141\u8a31\u7528\u6236\u6839\u64da\u7279\u5b9a\u689d\u4ef6\u8fd4\u56de\u4e0d\u540c\u7684\u503c\u3002\u5b83\u53ef\u4ee5\u5728SELECT\u3001UPDATE\u548cDELETE\u8a9e\u53e5\u4e2d\u4f7f\u7528\uff0c\u4e26\u4e14\u53ef\u4ee5\u7528\u4f86\u7c21\u5316\u8907\u96dc\u7684\u67e5\u8a62\u3002CASE\u8a9e\u53e5\u7684\u57fa\u672c\u8a9e\u6cd5\u5982\u4e0b\uff1a<\/p>\n<pre><code>\nCASE\n    WHEN condition1 THEN result1\n    WHEN condition2 THEN result2\n    ...\n    ELSE resultN\nEND\n<\/code><\/pre>\n<p>\u5728\u9019\u88e1\uff0c\u7576\u6eff\u8db3\u67d0\u500b\u689d\u4ef6\u6642\uff0cCASE\u8a9e\u53e5\u5c07\u8fd4\u56de\u76f8\u61c9\u7684\u7d50\u679c\u3002\u5982\u679c\u6c92\u6709\u4efb\u4f55\u689d\u4ef6\u6eff\u8db3\uff0c\u5247\u8fd4\u56deELSE\u90e8\u5206\u7684\u7d50\u679c\u3002<\/p>\n<h2 id=\"%e4%bd%bf%e7%94%a8case%e8%aa%9e%e5%8f%a5%e7%9a%84%e7%a4%ba%e4%be%8b-WaPBWFiBxu\">\u4f7f\u7528CASE\u8a9e\u53e5\u7684\u793a\u4f8b<\/h2>\n<p>\u4ee5\u4e0b\u662f\u4e00\u500b\u4f7f\u7528CASE\u8a9e\u53e5\u7684\u7c21\u55ae\u793a\u4f8b\u3002\u5047\u8a2d\u6211\u5011\u6709\u4e00\u500b\u540d\u70ba\u201cemployees\u201d\u7684\u8868\uff0c\u8a72\u8868\u5305\u542b\u54e1\u5de5\u7684\u59d3\u540d\u548c\u85aa\u6c34\u3002\u6211\u5011\u5e0c\u671b\u6839\u64da\u85aa\u6c34\u7684\u7bc4\u570d\u4f86\u5206\u985e\u54e1\u5de5\u7684\u85aa\u6c34\u7b49\u7d1a\u3002<\/p>\n<pre><code>\nSELECT name,\n       salary,\n       CASE\n           WHEN salary &lt; 30000 THEN &#039;\u4f4e\u85aa&#039;\n           WHEN salary BETWEEN 30000 AND 60000 THEN &#039;\u4e2d\u85aa&#039;\n           ELSE &#039;\u9ad8\u85aa&#039;\n       END AS salary_grade\nFROM employees;\n<\/code><\/pre>\n<p>\u5728\u9019\u500b\u67e5\u8a62\u4e2d\uff0c\u6211\u5011\u6839\u64da\u85aa\u6c34\u7684\u4e0d\u540c\u7bc4\u570d\u70ba\u6bcf\u4f4d\u54e1\u5de5\u5206\u914d\u4e86\u4e00\u500b\u85aa\u6c34\u7b49\u7d1a\u3002\u9019\u6a23\u7684\u67e5\u8a62\u4e0d\u50c5\u7c21\u5316\u4e86\u6578\u64da\u7684\u5448\u73fe\uff0c\u9084\u4f7f\u5f97\u6578\u64da\u7684\u5206\u6790\u8b8a\u5f97\u66f4\u52a0\u76f4\u89c0\u3002<\/p>\n<h2 id=\"case%e8%aa%9e%e5%8f%a5%e7%9a%84%e9%80%b2%e9%9a%8e%e7%94%a8%e6%b3%95-WaPBWFiBxu\">CASE\u8a9e\u53e5\u7684\u9032\u968e\u7528\u6cd5<\/h2>\n<p>\u9664\u4e86\u5728SELECT\u8a9e\u53e5\u4e2d\u4f7f\u7528\uff0cCASE\u8a9e\u53e5\u9084\u53ef\u4ee5\u5728UPDATE\u8a9e\u53e5\u4e2d\u4f7f\u7528\uff0c\u4ee5\u6839\u64da\u689d\u4ef6\u66f4\u65b0\u6578\u64da\u3002\u4f8b\u5982\uff0c\u5047\u8a2d\u6211\u5011\u60f3\u8981\u6839\u64da\u54e1\u5de5\u7684\u85aa\u6c34\u7b49\u7d1a\u4f86\u8abf\u6574\u85aa\u6c34\uff1a<\/p>\n<pre><code>\nUPDATE employees\nSET salary = CASE\n                 WHEN salary &lt; 30000 THEN salary * 1.1\n                 WHEN salary BETWEEN 30000 AND 60000 THEN salary * 1.05\n                 ELSE salary * 1.02\n             END;\n<\/code><\/pre>\n<p>\u5728\u9019\u500b\u4f8b\u5b50\u4e2d\uff0c\u6211\u5011\u6839\u64da\u4e0d\u540c\u7684\u85aa\u6c34\u7b49\u7d1a\u5c0d\u54e1\u5de5\u7684\u85aa\u6c34\u9032\u884c\u4e86\u8abf\u6574\u3002\u9019\u6a23\u7684\u64cd\u4f5c\u53ef\u4ee5\u5e6b\u52a9\u4f01\u696d\u6839\u64da\u5e02\u5834\u8b8a\u5316\u9748\u6d3b\u8abf\u6574\u85aa\u8cc7\u7d50\u69cb\u3002<\/p>\n<h2 id=\"%e6%b3%a8%e6%84%8f%e4%ba%8b%e9%a0%85-WaPBWFiBxu\">\u6ce8\u610f\u4e8b\u9805<\/h2>\n<p>\u5728\u4f7f\u7528CASE\u8a9e\u53e5\u6642\uff0c\u6709\u5e7e\u9ede\u9700\u8981\u6ce8\u610f\uff1a<\/p>\n<ul>\n<li>CASE\u8a9e\u53e5\u7684\u57f7\u884c\u9806\u5e8f\u662f\u5f9e\u4e0a\u5230\u4e0b\u7684\uff0c\u7b2c\u4e00\u500b\u6eff\u8db3\u689d\u4ef6\u7684\u7d50\u679c\u5c07\u88ab\u8fd4\u56de\u3002<\/li>\n<li>CASE\u8a9e\u53e5\u53ef\u4ee5\u5d4c\u5957\u4f7f\u7528\uff0c\u4f46\u904e\u591a\u7684\u5d4c\u5957\u53ef\u80fd\u6703\u5f71\u97ff\u67e5\u8a62\u7684\u53ef\u8b80\u6027\u3002<\/li>\n<li>\u5728\u4f7f\u7528ELSE\u90e8\u5206\u6642\uff0c\u5efa\u8b70\u63d0\u4f9b\u4e00\u500b\u9ed8\u8a8d\u503c\uff0c\u4ee5\u9632\u6240\u6709\u689d\u4ef6\u90fd\u4e0d\u6eff\u8db3\u3002<\/li>\n<\/ul>\n<h2 id=\"%e7%b8%bd%e7%b5%90-WaPBWFiBxu\">\u7e3d\u7d50<\/h2>\n<p>MySQL\u4e2d\u7684CASE\u8a9e\u53e5\u662f\u4e00\u500b\u5f37\u5927\u7684\u5de5\u5177\uff0c\u53ef\u4ee5\u5e6b\u52a9\u7528\u6236\u6839\u64da\u7279\u5b9a\u689d\u4ef6\u9032\u884c\u6578\u64da\u9078\u64c7\u548c\u66f4\u65b0\u3002\u901a\u904e\u5408\u7406\u4f7f\u7528CASE\u8a9e\u53e5\uff0c\u53ef\u4ee5\u7c21\u5316\u67e5\u8a62\u4e26\u63d0\u9ad8\u6578\u64da\u8655\u7406\u7684\u6548\u7387\u3002\u7121\u8ad6\u662f\u5728\u6578\u64da\u5206\u6790\u9084\u662f\u6578\u64da\u7ba1\u7406\u4e2d\uff0c\u638c\u63e1CASE\u8a9e\u53e5\u7684\u7528\u6cd5\u90fd\u662f\u975e\u5e38\u91cd\u8981\u7684\u3002<\/p>\n<p>\u5982\u679c\u60a8\u5c0d\u65bc\u6578\u64da\u5eab\u7ba1\u7406\u6709\u9032\u4e00\u6b65\u7684\u9700\u6c42\uff0c\u8003\u616e\u4f7f\u7528<a href=\"https:\/\/server.hk\">\u9999\u6e2fVPS<\/a>\u4f86\u642d\u5efa\u60a8\u7684\u6578\u64da\u5eab\u74b0\u5883\uff0c\u4eab\u53d7\u66f4\u9ad8\u7684\u6027\u80fd\u548c\u7a69\u5b9a\u6027\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u63a2\u7d22MySQL\u4e2d\u689d\u4ef6SELECT CASE\u7684\u5be6\u73fe\uff0c\u5b78\u7fd2\u5982\u4f55\u6839\u64da\u7279\u5b9a\u689d\u4ef6\u8fd4\u56de\u4e0d\u540c\u7d50\u679c\uff0c\u63d0\u5347\u67e5\u8a62\u9748\u6d3b\u6027\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-76868","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/76868","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=76868"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/76868\/revisions"}],"predecessor-version":[{"id":76869,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/76868\/revisions\/76869"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=76868"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=76868"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=76868"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}