{"id":200526,"date":"2025-05-06T11:16:58","date_gmt":"2025-05-06T03:16:58","guid":{"rendered":"https:\/\/server.hk\/cnblog\/200526\/"},"modified":"2025-05-06T11:16:58","modified_gmt":"2025-05-06T03:16:58","slug":"mysql-%e4%b8%ad-ifnull-%e4%b8%8e-nullif-%e5%b5%8c%e5%a5%97%e4%bd%bf%e7%94%a8%e4%bc%9a%e9%80%a0%e6%88%90%e6%80%a7%e8%83%bd%e6%8d%9f%e8%80%97%e5%90%97%ef%bc%9f","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/200526\/","title":{"rendered":"MySQL \u4e2d IFNULL() \u4e0e NULLIF() \u5d4c\u5957\u4f7f\u7528\u4f1a\u9020\u6210\u6027\u80fd\u635f\u8017\u5417\uff1f"},"content":{"rendered":"<p><b><\/b> <\/p>\n<h1>MySQL \u4e2d IFNULL() \u4e0e NULLIF() \u5d4c\u5957\u4f7f\u7528\u4f1a\u9020\u6210\u6027\u80fd\u635f\u8017\u5417\uff1f<\/h1>\n<p>\u4eb2\u7231\u7684\u7f16\u7a0b\u5b66\u4e60\u7231\u597d\u8005\uff0c\u5982\u679c\u4f60\u70b9\u5f00\u4e86\u8fd9\u7bc7\u6587\u7ae0\uff0c\u8bf4\u660e\u4f60\u5bf9\u300aMySQL \u4e2d IFNULL() \u4e0e NULLIF() \u5d4c\u5957\u4f7f\u7528\u4f1a\u9020\u6210\u6027\u80fd\u635f\u8017\u5417\uff1f\u300b\u5f88\u611f\u5174\u8da3\u3002\u672c\u7bc7\u6587\u7ae0\u5c31\u6765\u7ed9\u5927\u5bb6\u8be6\u7ec6\u89e3\u6790\u4e00\u4e0b\uff0c\u4e3b\u8981\u4ecb\u7ecd\u4e00\u4e0b\uff0c\u5e0c\u671b\u6240\u6709\u8ba4\u771f\u8bfb\u5b8c\u7684\u7ae5\u978b\u4eec\uff0c\u90fd\u6709\u5b9e\u8d28\u6027\u7684\u63d0\u9ad8\u3002<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/www.17golang.com\/uploads\/20241107\/1730973108672c8db43aacf.jpg\" class=\"aligncenter\"><\/p>\n<p><strong>ifnull()\u4e0enullif()\u5d4c\u5957\u5bfc\u81f4\u7684\u6027\u80fd\u635f\u8017<\/strong><\/p>\n<p>\u5728 mysql \u4e2d\u4f7f\u7528 jpa \u62fc\u63a5\u52a8\u6001\u6761\u4ef6 sql \u65f6\uff0c\u4f7f\u7528 ifnull(nullif(?1,&#8221;),&#8217;xxx\u5b57\u6bb5&#8217;) \u8fd9\u6837\u7684\u5d4c\u5957\u51fd\u6570\u53ef\u80fd\u5b58\u5728\u6027\u80fd\u635f\u8017\u3002<\/p>\n<p>\u5f53 nullif(?1,&#8221;) \u9047\u7a7a\u503c\u65f6\uff0c\u5b83\u4f1a\u8fd4\u56de\u7a7a\u5b57\u7b26\u4e32\u3002\u7136\u540e\uff0c\u5916\u5c42\u7684 ifnull() \u51fd\u6570\u5c06\u6b64\u7a7a\u5b57\u7b26\u4e32\u4e0e &#8216;xxx\u5b57\u6bb5&#8217; \u8fdb\u884c\u6bd4\u8f83\uff0c\u7ed3\u679c\u59cb\u7ec8\u4e3a\u771f\u3002\u56e0\u6b64\uff0c\u5b9e\u9645\u6267\u884c\u7684 sql \u8bed\u53e5\u76f8\u5f53\u4e8e where xxx\u5b57\u6bb5=xxx\u5b57\u6bb5\uff0c\u8fd9\u662f\u4e00\u79cd\u5197\u4f59\u4e14\u4e0d\u5fc5\u8981\u7684\u68c0\u67e5\u3002<\/p>\n<p>\u8fd9\u79cd\u505a\u6cd5\u4e0d\u4ec5\u5bf9\u6027\u80fd\u6709\u5bb3\uff0c\u8fd8\u4f1a\u589e\u52a0\u4ee3\u7801\u7684\u53ef\u7ef4\u62a4\u6027\u3002\u76f8\u53cd\uff0c\u5e94\u4f7f\u7528\u4ee3\u7801\u6765\u63a7\u5236\u6b64\u7c7b\u9700\u6c42\uff0c\u4f8b\u5982\uff1a<\/p>\n<pre>if (parameter != null) {\n  query.where(\"xxx\u5b57\u6bb5 = :xxx\u5b57\u6bb5\").setParameter(\"xxx\u5b57\u6bb5\", parameter);\n}<\/pre>\n<p>\u907f\u514d\u5728\u6570\u636e\u5e93\u8868\u8bbe\u8ba1\u4e2d\u4f7f\u7528 null \u503c\u4e5f\u6709\u52a9\u4e8e\u63d0\u9ad8\u6027\u80fd\u3002<\/p>\n<p>\u5230\u8fd9\u91cc\uff0c\u6211\u4eec\u4e5f\u5c31\u8bb2\u5b8c\u4e86\u300aMySQL \u4e2d IFNULL() \u4e0e NULLIF() \u5d4c\u5957\u4f7f\u7528\u4f1a\u9020\u6210\u6027\u80fd\u635f\u8017\u5417\uff1f\u300b\u7684\u5185\u5bb9\u4e86\u3002\u4e2a\u4eba\u8ba4\u4e3a\uff0c\u57fa\u7840\u77e5\u8bc6\u7684\u5b66\u4e60\u548c\u5de9\u56fa\uff0c\u662f\u4e3a\u4e86\u66f4\u597d\u7684\u5c06\u5176\u8fd0\u7528\u5230\u9879\u76ee\u4e2d\uff0c\u6b22\u8fce\u5173\u6ce8\u4e3b\u673a\u5b9d\u8d1d\u516c\u4f17\u53f7\uff0c\u5e26\u4f60\u4e86\u89e3\u66f4\u591a\u5173\u4e8e\u7684\u77e5\u8bc6\u70b9\uff01<\/p>\n<dl>\n<dt>\n <\/dt>\n<\/dl>\n","protected":false},"excerpt":{"rendered":"<p>MySQL \u4e2d IFNULL()&#46;&#46;&#46;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[101],"tags":[],"class_list":["post-200526","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/200526","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"}],"author":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/comments?post=200526"}],"version-history":[{"count":0,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/200526\/revisions"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=200526"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=200526"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=200526"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}