{"id":187694,"date":"2024-11-11T16:24:21","date_gmt":"2024-11-11T08:24:21","guid":{"rendered":"https:\/\/server.hk\/cnblog\/187694\/"},"modified":"2024-11-11T16:24:22","modified_gmt":"2024-11-11T08:24:22","slug":"%e6%95%b8%e6%93%9a%e5%ba%ab%e4%b8%adif%e6%a2%9d%e4%bb%b6%e8%aa%9e%e5%8f%a5%e7%9a%84%e6%af%94%e8%bc%83%ef%bc%9a%e6%8e%8c%e6%8f%a1%e6%96%b9%e6%b3%95%e6%8f%90%e9%ab%98%e6%95%88%e7%8e%87-%e6%95%b8","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/187694\/","title":{"rendered":"\u6578\u64da\u5eab\u4e2dif\u689d\u4ef6\u8a9e\u53e5\u7684\u6bd4\u8f03\uff1a\u638c\u63e1\u65b9\u6cd5\u63d0\u9ad8\u6548\u7387 (\u6578\u64da\u5eab if\u689d\u4ef6\u8a9e\u53e5\u6bd4\u8f03)"},"content":{"rendered":"<h1 id=\"%e6%95%b8%e6%93%9a%e5%ba%ab%e4%b8%adif%e6%a2%9d%e4%bb%b6%e8%aa%9e%e5%8f%a5%e7%9a%84%e6%af%94%e8%bc%83%ef%bc%9a%e6%8e%8c%e6%8f%a1%e6%96%b9%e6%b3%95%e6%8f%90%e9%ab%98%e6%95%88%e7%8e%87-GHmuzpBxVl\">\u6578\u64da\u5eab\u4e2dif\u689d\u4ef6\u8a9e\u53e5\u7684\u6bd4\u8f03\uff1a\u638c\u63e1\u65b9\u6cd5\u63d0\u9ad8\u6548\u7387<\/h1>\n<p>\u5728\u6578\u64da\u5eab\u7ba1\u7406\u4e2d\uff0c\u689d\u4ef6\u8a9e\u53e5\u662f\u975e\u5e38\u91cd\u8981\u7684\u5de5\u5177\uff0c\u5c24\u5176\u662f <code>IF<\/code> \u689d\u4ef6\u8a9e\u53e5\u3002\u5b83\u5011\u80fd\u5920\u5e6b\u52a9\u958b\u767c\u8005\u6839\u64da\u7279\u5b9a\u689d\u4ef6\u57f7\u884c\u4e0d\u540c\u7684\u64cd\u4f5c\u3002\u672c\u6587\u5c07\u63a2\u8a0e\u6578\u64da\u5eab\u4e2d <code>IF<\/code> \u689d\u4ef6\u8a9e\u53e5\u7684\u4e0d\u540c\u5be6\u73fe\u65b9\u5f0f\uff0c\u4e26\u6bd4\u8f03\u5b83\u5011\u7684\u6548\u7387\uff0c\u4ee5\u5e6b\u52a9\u958b\u767c\u8005\u9078\u64c7\u6700\u5408\u9069\u7684\u65b9\u6cd5\u3002<\/p>\n<h2 id=\"if-%e6%a2%9d%e4%bb%b6%e8%aa%9e%e5%8f%a5%e7%9a%84%e5%9f%ba%e6%9c%ac%e6%a6%82%e5%bf%b5-GHmuzpBxVl\">IF \u689d\u4ef6\u8a9e\u53e5\u7684\u57fa\u672c\u6982\u5ff5<\/h2>\n<p><code>IF<\/code> \u689d\u4ef6\u8a9e\u53e5\u901a\u5e38\u7528\u65bc\u6839\u64da\u67d0\u4e9b\u689d\u4ef6\u57f7\u884c\u4e0d\u540c\u7684 SQL \u8a9e\u53e5\u3002\u9019\u4e9b\u689d\u4ef6\u53ef\u4ee5\u662f\u6578\u64da\u5eab\u4e2d\u7684\u5b57\u6bb5\u503c\u3001\u8a08\u7b97\u7d50\u679c\u6216\u5176\u4ed6\u908f\u8f2f\u5224\u65b7\u3002\u6839\u64da\u4e0d\u540c\u7684\u6578\u64da\u5eab\u7cfb\u7d71\uff0c<code>IF<\/code> \u689d\u4ef6\u8a9e\u53e5\u7684\u8a9e\u6cd5\u548c\u529f\u80fd\u53ef\u80fd\u6703\u6709\u6240\u4e0d\u540c\u3002<\/p>\n<h2 id=\"%e4%b8%8d%e5%90%8c%e6%95%b8%e6%93%9a%e5%ba%ab%e7%b3%bb%e7%b5%b1%e4%b8%ad%e7%9a%84-if-%e6%a2%9d%e4%bb%b6%e8%aa%9e%e5%8f%a5-GHmuzpBxVl\">\u4e0d\u540c\u6578\u64da\u5eab\u7cfb\u7d71\u4e2d\u7684 IF \u689d\u4ef6\u8a9e\u53e5<\/h2>\n<h3 id=\"1-mysql-GHmuzpBxVl\">1. MySQL<\/h3>\n<p>\u5728 MySQL \u4e2d\uff0c<code>IF<\/code> \u689d\u4ef6\u8a9e\u53e5\u7684\u57fa\u672c\u8a9e\u6cd5\u5982\u4e0b\uff1a<\/p>\n<pre><code>SELECT IF(condition, true_value, false_value);\n<\/code><\/pre>\n<p>\u4f8b\u5982\uff0c\u5047\u8a2d\u6211\u5011\u6709\u4e00\u500b\u540d\u70ba <code>employees<\/code> \u7684\u8868\uff0c\u4e26\u5e0c\u671b\u6839\u64da\u54e1\u5de5\u7684\u85aa\u6c34\u4f86\u5224\u65b7\u5176\u7b49\u7d1a\uff1a<\/p>\n<pre><code>SELECT name, IF(salary &gt; 50000, '\u9ad8\u7d1a', '\u521d\u7d1a') AS level FROM employees;\n<\/code><\/pre>\n<h3 id=\"2-sql-server-GHmuzpBxVl\">2. SQL Server<\/h3>\n<p>\u5728 SQL Server \u4e2d\uff0c<code>IF<\/code> \u689d\u4ef6\u8a9e\u53e5\u7684\u4f7f\u7528\u65b9\u5f0f\u7565\u6709\u4e0d\u540c\u3002\u5b83\u901a\u5e38\u7528\u65bc\u63a7\u5236\u6d41\u7a0b\uff0c\u800c\u4e0d\u662f\u5728\u67e5\u8a62\u4e2d\u76f4\u63a5\u4f7f\u7528\u3002\u5176\u57fa\u672c\u8a9e\u6cd5\u5982\u4e0b\uff1a<\/p>\n<pre><code>IF condition\nBEGIN\n    -- SQL \u8a9e\u53e5\nEND\nELSE\nBEGIN\n    -- \u5176\u4ed6 SQL \u8a9e\u53e5\nEND\n<\/code><\/pre>\n<p>\u4f8b\u5982\uff1a<\/p>\n<pre><code>IF (SELECT COUNT(*) FROM employees WHERE salary &gt; 50000) &gt; 0\nBEGIN\n    PRINT '\u6709\u9ad8\u7d1a\u54e1\u5de5';\nEND\nELSE\nBEGIN\n    PRINT '\u6c92\u6709\u9ad8\u7d1a\u54e1\u5de5';\nEND\n<\/code><\/pre>\n<h3 id=\"3-postgresql-GHmuzpBxVl\">3. PostgreSQL<\/h3>\n<p>\u5728 PostgreSQL \u4e2d\uff0c<code>IF<\/code> \u689d\u4ef6\u8a9e\u53e5\u901a\u5e38\u7528\u65bc\u51fd\u6578\u5167\u90e8\u3002\u5176\u8a9e\u6cd5\u5982\u4e0b\uff1a<\/p>\n<pre><code>IF condition THEN\n    -- SQL \u8a9e\u53e5\nEND IF;\n<\/code><\/pre>\n<p>\u4f8b\u5982\uff1a<\/p>\n<pre><code>CREATE OR REPLACE FUNCTION check_salary() RETURNS VOID AS $$\nBEGIN\n    IF (SELECT COUNT(*) FROM employees WHERE salary &gt; 50000) &gt; 0 THEN\n        RAISE NOTICE '\u6709\u9ad8\u7d1a\u54e1\u5de5';\n    ELSE\n        RAISE NOTICE '\u6c92\u6709\u9ad8\u7d1a\u54e1\u5de5';\n    END IF;\nEND;\n$$ LANGUAGE plpgsql;\n<\/code><\/pre>\n<h2 id=\"%e6%95%88%e7%8e%87%e6%af%94%e8%bc%83-GHmuzpBxVl\">\u6548\u7387\u6bd4\u8f03<\/h2>\n<p>\u5728\u9078\u64c7\u4f7f\u7528 <code>IF<\/code> \u689d\u4ef6\u8a9e\u53e5\u6642\uff0c\u6548\u7387\u662f\u958b\u767c\u8005\u9700\u8981\u8003\u616e\u7684\u91cd\u8981\u56e0\u7d20\u3002\u4ee5\u4e0b\u662f\u5e7e\u500b\u5f71\u97ff\u6548\u7387\u7684\u56e0\u7d20\uff1a<\/p>\n<ul>\n<li><strong>\u57f7\u884c\u8a08\u5283\uff1a<\/strong>\u4e0d\u540c\u7684\u6578\u64da\u5eab\u7cfb\u7d71\u5728\u8655\u7406 <code>IF<\/code> \u689d\u4ef6\u8a9e\u53e5\u6642\uff0c\u53ef\u80fd\u6703\u751f\u6210\u4e0d\u540c\u7684\u57f7\u884c\u8a08\u5283\uff0c\u9019\u6703\u5f71\u97ff\u67e5\u8a62\u7684\u6027\u80fd\u3002<\/li>\n<li><strong>\u6578\u64da\u91cf\uff1a<\/strong>\u7576\u6578\u64da\u91cf\u8f03\u5927\u6642\uff0c\u4f7f\u7528 <code>IF<\/code> \u689d\u4ef6\u8a9e\u53e5\u53ef\u80fd\u6703\u5c0e\u81f4\u6027\u80fd\u4e0b\u964d\uff0c\u7279\u5225\u662f\u5728\u9700\u8981\u591a\u6b21\u8a55\u4f30\u689d\u4ef6\u7684\u60c5\u6cc1\u4e0b\u3002<\/li>\n<li><strong>\u7d22\u5f15\u4f7f\u7528\uff1a<\/strong>\u5408\u7406\u4f7f\u7528\u7d22\u5f15\u53ef\u4ee5\u986f\u8457\u63d0\u9ad8\u67e5\u8a62\u6548\u7387\uff0c\u7279\u5225\u662f\u5728\u6d89\u53ca\u5230\u689d\u4ef6\u5224\u65b7\u7684\u67e5\u8a62\u4e2d\u3002<\/li>\n<\/ul>\n<h2 id=\"%e7%b5%90%e8%ab%96-GHmuzpBxVl\">\u7d50\u8ad6<\/h2>\n<p>\u5728\u6578\u64da\u5eab\u4e2d\u4f7f\u7528 <code>IF<\/code> \u689d\u4ef6\u8a9e\u53e5\u662f\u4e00\u7a2e\u5f37\u5927\u7684\u5de5\u5177\uff0c\u53ef\u4ee5\u6839\u64da\u4e0d\u540c\u7684\u689d\u4ef6\u57f7\u884c\u4e0d\u540c\u7684\u64cd\u4f5c\u3002\u4e0d\u540c\u7684\u6578\u64da\u5eab\u7cfb\u7d71\u5c0d <code>IF<\/code> \u689d\u4ef6\u8a9e\u53e5\u7684\u652f\u6301\u548c\u5be6\u73fe\u65b9\u5f0f\u5404\u6709\u4e0d\u540c\uff0c\u958b\u767c\u8005\u61c9\u6839\u64da\u5177\u9ad4\u9700\u6c42\u9078\u64c7\u5408\u9069\u7684\u5be6\u73fe\u65b9\u5f0f\u3002\u540c\u6642\uff0c\u8003\u616e\u5230\u6548\u7387\u554f\u984c\uff0c\u5408\u7406\u8a2d\u8a08\u67e5\u8a62\u548c\u4f7f\u7528\u7d22\u5f15\u5c07\u6709\u52a9\u65bc\u63d0\u9ad8\u6027\u80fd\u3002<\/p>\n<p>\u5982\u9700\u4e86\u89e3\u66f4\u591a\u95dc\u65bc <a href=\"https:\/\/server.hk\">\u9999\u6e2fVPS<\/a> \u548c\u6578\u64da\u5eab\u7ba1\u7406\u7684\u8cc7\u8a0a\uff0c\u8acb\u8a2a\u554f\u6211\u5011\u7684\u7db2\u7ad9\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u6bd4\u8f03\u6578\u64da\u5eab\u4e2d\u7684if\u689d\u4ef6\u8a9e\u53e5\uff0c\u638c\u63e1\u9ad8\u6548\u65b9\u6cd5\uff0c\u63d0\u5347\u67e5\u8a62\u6027\u80fd\uff0c\u512a\u5316\u6578\u64da\u8655\u7406\u6d41\u7a0b\uff0c\u52a9\u529b\u6578\u64da\u5206\u6790\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-187694","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/187694","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=187694"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/187694\/revisions"}],"predecessor-version":[{"id":187695,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/187694\/revisions\/187695"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=187694"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=187694"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=187694"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}