{"id":193405,"date":"2024-11-12T21:54:22","date_gmt":"2024-11-12T13:54:22","guid":{"rendered":"https:\/\/server.hk\/cnblog\/193405\/"},"modified":"2024-11-12T21:54:23","modified_gmt":"2024-11-12T13:54:23","slug":"%e5%ad%b8%e6%9c%83%e6%95%b8%e6%93%9a%e5%ba%ab%e8%aa%9e%e5%8f%a5%e4%b8%ad%e7%9a%84case%e6%a2%9d%e4%bb%b6%e5%88%a4%e6%96%b7-%e6%95%b8%e6%93%9a%e5%ba%ab%e8%aa%9e%e5%8f%a5case","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/193405\/","title":{"rendered":"\u5b78\u6703\u6578\u64da\u5eab\u8a9e\u53e5\u4e2d\u7684case\u689d\u4ef6\u5224\u65b7 (\u6578\u64da\u5eab\u8a9e\u53e5case)"},"content":{"rendered":"<h1 id=\"%e5%ad%b8%e6%9c%83%e6%95%b8%e6%93%9a%e5%ba%ab%e8%aa%9e%e5%8f%a5%e4%b8%ad%e7%9a%84case%e6%a2%9d%e4%bb%b6%e5%88%a4%e6%96%b7-eWZvPEpOln\">\u5b78\u6703\u6578\u64da\u5eab\u8a9e\u53e5\u4e2d\u7684CASE\u689d\u4ef6\u5224\u65b7<\/h1>\n<p>\u5728\u6578\u64da\u5eab\u7ba1\u7406\u7cfb\u7d71\u4e2d\uff0cCASE\u8a9e\u53e5\u662f\u4e00\u500b\u975e\u5e38\u6709\u7528\u7684\u5de5\u5177\uff0c\u80fd\u5920\u6839\u64da\u4e0d\u540c\u7684\u689d\u4ef6\u8fd4\u56de\u4e0d\u540c\u7684\u7d50\u679c\u3002\u9019\u4f7f\u5f97\u6578\u64da\u67e5\u8a62\u66f4\u52a0\u9748\u6d3b\u548c\u5f37\u5927\u3002\u672c\u6587\u5c07\u6df1\u5165\u63a2\u8a0eCASE\u8a9e\u53e5\u7684\u57fa\u672c\u7528\u6cd5\u3001\u5be6\u969b\u61c9\u7528\u4ee5\u53ca\u4e00\u4e9b\u793a\u4f8b\uff0c\u5e6b\u52a9\u8b80\u8005\u66f4\u597d\u5730\u7406\u89e3\u548c\u904b\u7528\u9019\u4e00\u529f\u80fd\u3002<\/p>\n<h2 id=\"case%e8%aa%9e%e5%8f%a5%e7%9a%84%e5%9f%ba%e6%9c%ac%e7%b5%90%e6%a7%8b-eWZvPEpOln\">CASE\u8a9e\u53e5\u7684\u57fa\u672c\u7d50\u69cb<\/h2>\n<p>CASE\u8a9e\u53e5\u7684\u57fa\u672c\u7d50\u69cb\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\u500b\u7d50\u69cb\u4e2d\uff0c<code>condition<\/code>\u662f\u9700\u8981\u8a55\u4f30\u7684\u689d\u4ef6\uff0c\u800c<code>result<\/code>\u5247\u662f\u7576\u689d\u4ef6\u6210\u7acb\u6642\u8fd4\u56de\u7684\u7d50\u679c\u3002\u7576\u6240\u6709\u689d\u4ef6\u90fd\u4e0d\u6210\u7acb\u6642\uff0c\u5c07\u8fd4\u56de<code>ELSE<\/code>\u5f8c\u7684\u7d50\u679c\u3002\u5982\u679c\u6c92\u6709<code>ELSE<\/code>\u90e8\u5206\uff0c\u5247\u5728\u6240\u6709\u689d\u4ef6\u4e0d\u6210\u7acb\u6642\u8fd4\u56de<code>NULL<\/code>\u3002<\/p>\n<h2 id=\"case%e8%aa%9e%e5%8f%a5%e7%9a%84%e4%bd%bf%e7%94%a8%e5%a0%b4%e6%99%af-eWZvPEpOln\">CASE\u8a9e\u53e5\u7684\u4f7f\u7528\u5834\u666f<\/h2>\n<p>CASE\u8a9e\u53e5\u53ef\u4ee5\u5728\u591a\u7a2e\u60c5\u6cc1\u4e0b\u4f7f\u7528\uff0c\u4ee5\u4e0b\u662f\u4e00\u4e9b\u5e38\u898b\u7684\u61c9\u7528\u5834\u666f\uff1a<\/p>\n<ul>\n<li><strong>\u6578\u64da\u5206\u985e\uff1a<\/strong>\u6839\u64da\u67d0\u4e9b\u689d\u4ef6\u5c07\u6578\u64da\u5206\u7d44\u6216\u5206\u985e\u3002<\/li>\n<li><strong>\u8a08\u7b97\u884d\u751f\u5b57\u6bb5\uff1a<\/strong>\u6839\u64da\u4e0d\u540c\u7684\u689d\u4ef6\u8a08\u7b97\u65b0\u7684\u5b57\u6bb5\u503c\u3002<\/li>\n<li><strong>\u6578\u64da\u8f49\u63db\uff1a<\/strong>\u5c07\u6578\u64da\u5f9e\u4e00\u7a2e\u683c\u5f0f\u8f49\u63db\u70ba\u53e6\u4e00\u7a2e\u683c\u5f0f\u3002<\/li>\n<\/ul>\n<h2 id=\"%e5%af%a6%e9%9a%9b%e7%a4%ba%e4%be%8b-eWZvPEpOln\">\u5be6\u969b\u793a\u4f8b<\/h2>\n<p>\u4ee5\u4e0b\u662f\u4e00\u500b\u4f7f\u7528CASE\u8a9e\u53e5\u7684\u5be6\u969b\u793a\u4f8b\uff0c\u5047\u8a2d\u6211\u5011\u6709\u4e00\u500b\u540d\u70ba<code>employees<\/code>\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  60000 THEN '\u9ad8\u85aa'\n           ELSE '\u672a\u77e5'\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\u80fd\u5920\u63d0\u4f9b\u66f4\u6e05\u6670\u7684\u6578\u64da\u8996\u5716\uff0c\u9084\u80fd\u5e6b\u52a9\u7ba1\u7406\u5c64\u505a\u51fa\u66f4\u660e\u667a\u7684\u6c7a\u7b56\u3002<\/p>\n<h2 id=\"%e5%a4%9a%e9%87%8dcase%e8%aa%9e%e5%8f%a5-eWZvPEpOln\">\u591a\u91cdCASE\u8a9e\u53e5<\/h2>\n<p>\u5728\u67d0\u4e9b\u60c5\u6cc1\u4e0b\uff0c\u6211\u5011\u53ef\u80fd\u9700\u8981\u5728\u4e00\u500b\u67e5\u8a62\u4e2d\u4f7f\u7528\u591a\u500bCASE\u8a9e\u53e5\u3002\u4ee5\u4e0b\u662f\u4e00\u500b\u793a\u4f8b\uff0c\u5c55\u793a\u5982\u4f55\u5728\u4e00\u500b\u67e5\u8a62\u4e2d\u4f7f\u7528\u591a\u500bCASE\u8a9e\u53e5\u4f86\u8a08\u7b97\u4e0d\u540c\u7684\u734e\u91d1\uff1a<\/p>\n<pre><code>\nSELECT name,\n       salary,\n       CASE\n           WHEN salary &lt; 30000 THEN salary * 0.1\n           WHEN salary BETWEEN 30000 AND 60000 THEN salary * 0.05\n           ELSE 0\n       END AS bonus\nFROM employees;\n<\/code><\/pre>\n<p>\u5728\u9019\u500b\u67e5\u8a62\u4e2d\uff0c\u6211\u5011\u6839\u64da\u54e1\u5de5\u7684\u85aa\u6c34\u8a08\u7b97\u734e\u91d1\uff0c\u4e26\u5c07\u7d50\u679c\u4f5c\u70ba\u4e00\u500b\u65b0\u5b57\u6bb5\u8fd4\u56de\u3002\u9019\u6a23\u7684\u67e5\u8a62\u53ef\u4ee5\u5e6b\u52a9\u4f01\u696d\u6839\u64da\u4e0d\u540c\u7684\u85aa\u6c34\u6c34\u5e73\u5236\u5b9a\u76f8\u61c9\u7684\u734e\u91d1\u653f\u7b56\u3002<\/p>\n<h2 id=\"%e7%b8%bd%e7%b5%90-eWZvPEpOln\">\u7e3d\u7d50<\/h2>\n<p>CASE\u8a9e\u53e5\u5728\u6578\u64da\u5eab\u67e5\u8a62\u4e2d\u662f\u4e00\u500b\u5f37\u5927\u7684\u5de5\u5177\uff0c\u80fd\u5920\u6839\u64da\u4e0d\u540c\u7684\u689d\u4ef6\u8fd4\u56de\u4e0d\u540c\u7684\u7d50\u679c\u3002\u901a\u904e\u9748\u6d3b\u904b\u7528CASE\u8a9e\u53e5\uff0c\u958b\u767c\u8005\u53ef\u4ee5\u66f4\u6709\u6548\u5730\u8655\u7406\u6578\u64da\uff0c\u9032\u884c\u5206\u985e\u548c\u8a08\u7b97\u3002\u7121\u8ad6\u662f\u5728\u6578\u64da\u5206\u6790\u9084\u662f\u5831\u544a\u751f\u6210\u4e2d\uff0c\u638c\u63e1CASE\u8a9e\u53e5\u7684\u4f7f\u7528\u90fd\u5c07\u5927\u5927\u63d0\u9ad8\u5de5\u4f5c\u6548\u7387\u3002<\/p>\n<p>\u5982\u679c\u60a8\u5c0d\u65bc\u6578\u64da\u5eab\u7ba1\u7406\u6216\u5176\u4ed6\u6280\u8853\u554f\u984c\u6709\u8208\u8da3\uff0c\u6b61\u8fce\u8a2a\u554f\u6211\u5011\u7684\u7db2\u7ad9\u4e86\u89e3\u66f4\u591a\u8cc7\u8a0a\uff0c\u7279\u5225\u662f\u6211\u5011\u63d0\u4f9b\u7684<a href=\"https:\/\/server.hk\">\u9999\u6e2fVPS<\/a>\u548c<a href=\"https:\/\/server.hk\">\u96f2\u4f3a\u670d\u5668<\/a>\u89e3\u6c7a\u65b9\u6848\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u5b78\u6703\u5982\u4f55\u5728\u6578\u64da\u5eab\u8a9e\u53e5\u4e2d\u4f7f\u7528CASE\u689d\u4ef6\u5224\u65b7\uff0c\u63d0\u5347\u67e5\u8a62\u9748\u6d3b\u6027\u8207\u6548\u7387\uff0c\u8f15\u9b06\u8655\u7406\u591a\u7a2e\u6578\u64da\u60c5\u5883\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-193405","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/193405","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=193405"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/193405\/revisions"}],"predecessor-version":[{"id":193406,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/193405\/revisions\/193406"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=193405"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=193405"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=193405"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}