{"id":25647,"date":"2024-11-24T14:19:31","date_gmt":"2024-11-24T06:19:31","guid":{"rendered":"https:\/\/fwq.ai\/blog\/25647\/"},"modified":"2024-11-24T14:19:31","modified_gmt":"2024-11-24T06:19:31","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-2","status":"publish","type":"post","link":"https:\/\/fwq.ai\/blog\/25647\/","title":{"rendered":"MySQL \u4e2d IFNULL() \u4e0e NULLIF() \u5d4c\u5957\u4f7f\u7528\u4f1a\u9020\u6210\u6027\u80fd\u635f\u8017\u5417\uff1f"},"content":{"rendered":"<p><img decoding=\"async\" src=\"https:\/\/img.php.cn\/upload\/article\/001\/246\/273\/173064474416700.jpg\" class=\"aligncenter\" title=\"MySQL \u4e2d IFNULL() \u4e0e NULLIF() \u5d4c\u5957\u4f7f\u7528\u4f1a\u9020\u6210\u6027\u80fd\u635f\u8017\u5417\uff1f\u63d2\u56fe\" alt=\"MySQL \u4e2d IFNULL() \u4e0e NULLIF() \u5d4c\u5957\u4f7f\u7528\u4f1a\u9020\u6210\u6027\u80fd\u635f\u8017\u5417\uff1f\u63d2\u56fe\" \/><\/p>\n<p><strong>ifnull()\u4e0enullif()\u5d4c\u5957\u5bfc\u81f4\u7684\u6027\u80fd\u635f\u8017<\/strong><\/p>\n<p>\u5728  \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> \u767b\u5f55\u540e\u590d\u5236 <\/p>\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>\u4ee5\u4e0a\u5c31\u662fMySQL \u4e2d IFNULL() \u4e0e NULLIF() \u5d4c\u5957\u4f7f\u7528\u4f1a\u9020\u6210\u6027\u80fd\u635f\u8017\u5417\uff1f\u7684\u8be6\u7ec6\u5185\u5bb9\uff0c\u66f4\u591a\u8bf7\u5173\u6ce8\u7c73\u4e91\u5176\u5b83\u76f8\u5173\u6587\u7ae0\uff01<\/p>\n","protected":false},"excerpt":{"rendered":"<p>ifnull()\u4e0enullif()\u5d4c\u5957\u5bfc\u81f4\u7684\u6027\u80fd\u635f\u8017 \u5728 \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 \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 \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 if (parameter != null) { query.where(&#8220;xxx\u5b57\u6bb5 = :xxx\u5b57\u6bb5&#8221;).setParameter(&#8220;xxx\u5b57\u6bb5&#8221;, parameter); } \u767b\u5f55\u540e\u590d\u5236 \u907f\u514d\u5728\u6570\u636e\u5e93\u8868\u8bbe\u8ba1\u4e2d\u4f7f\u7528 null \u503c\u4e5f\u6709\u52a9\u4e8e\u63d0\u9ad8\u6027\u80fd\u3002 \u4ee5\u4e0a\u5c31\u662fMySQL \u4e2d IFNULL() \u4e0e NULLIF() \u5d4c\u5957\u4f7f\u7528\u4f1a\u9020\u6210\u6027\u80fd\u635f\u8017\u5417\uff1f\u7684\u8be6\u7ec6\u5185\u5bb9\uff0c\u66f4\u591a\u8bf7\u5173\u6ce8\u7c73\u4e91\u5176\u5b83\u76f8\u5173\u6587\u7ae0\uff01<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[16],"tags":[],"class_list":["post-25647","post","type-post","status-publish","format-standard","hentry","category-16"],"_links":{"self":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/25647","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/comments?post=25647"}],"version-history":[{"count":0,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/25647\/revisions"}],"wp:attachment":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/media?parent=25647"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/categories?post=25647"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/tags?post=25647"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}