{"id":78774,"date":"2024-10-16T12:19:09","date_gmt":"2024-10-16T04:19:09","guid":{"rendered":"https:\/\/server.hk\/cnblog\/78774\/"},"modified":"2024-10-16T12:19:09","modified_gmt":"2024-10-16T04:19:09","slug":"mysql%e6%8c%87%e4%bb%a4-is-null%ef%bc%88%e7%82%ba%e7%a9%ba%ef%bc%89","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/78774\/","title":{"rendered":"MySQL\u6307\u4ee4: IS NULL\uff08\u70ba\u7a7a\uff09"},"content":{"rendered":"<h1 id=\"mysql%e6%8c%87%e4%bb%a4-is-null%ef%bc%88%e7%82%ba%e7%a9%ba%ef%bc%89-GaERDoziVV\">MySQL\u6307\u4ee4: IS NULL\uff08\u70ba\u7a7a\uff09<\/h1>\n<p>\u5728\u8cc7\u6599\u5eab\u7ba1\u7406\u7cfb\u7d71\u4e2d\uff0cMySQL\u662f\u4e00\u500b\u5ee3\u6cdb\u4f7f\u7528\u7684\u95dc\u806f\u5f0f\u8cc7\u6599\u5eab\u7ba1\u7406\u7cfb\u7d71\u3002\u7576\u6211\u5011\u8655\u7406\u8cc7\u6599\u6642\uff0c\u7d93\u5e38\u6703\u9047\u5230\u7a7a\u503c\uff08NULL\uff09\u7684\u60c5\u6cc1\u3002NULL\u5728MySQL\u4e2d\u4ee3\u8868\u8457\u7f3a\u5931\u7684\u6578\u64da\u6216\u672a\u77e5\u7684\u6578\u64da\u3002\u70ba\u4e86\u6709\u6548\u5730\u67e5\u8a62\u9019\u4e9b\u7a7a\u503c\uff0c\u6211\u5011\u53ef\u4ee5\u4f7f\u7528IS NULL\u6307\u4ee4\u3002\u672c\u6587\u5c07\u6df1\u5165\u63a2\u8a0eIS NULL\u7684\u7528\u6cd5\u53ca\u5176\u5728\u5be6\u969b\u61c9\u7528\u4e2d\u7684\u91cd\u8981\u6027\u3002<\/p>\n<h2 id=\"%e4%bb%80%e9%ba%bc%e6%98%afnull%ef%bc%9f-GaERDoziVV\">\u4ec0\u9ebc\u662fNULL\uff1f<\/h2>\n<p>\u5728MySQL\u4e2d\uff0cNULL\u662f\u4e00\u500b\u7279\u6b8a\u7684\u6a19\u8a18\uff0c\u7528\u4f86\u8868\u793a\u4e00\u500b\u503c\u7684\u7f3a\u5931\u3002\u9019\u8207\u7a7a\u5b57\u7b26\u4e32\u6216\u6578\u5b570\u4e0d\u540c\uff0c\u56e0\u70baNULL\u8868\u793a\u201c\u6c92\u6709\u503c\u201d\u3002\u5728\u8cc7\u6599\u5eab\u4e2d\uff0cNULL\u53ef\u4ee5\u51fa\u73fe\u5728\u4efb\u4f55\u6578\u64da\u985e\u578b\u7684\u6b04\u4f4d\u4e2d\uff0c\u5305\u62ec\u6574\u6578\u3001\u6d6e\u9ede\u6578\u3001\u5b57\u7b26\u4e32\u7b49\u3002<\/p>\n<h2 id=\"is-null%e7%9a%84%e5%9f%ba%e6%9c%ac%e7%94%a8%e6%b3%95-GaERDoziVV\">IS NULL\u7684\u57fa\u672c\u7528\u6cd5<\/h2>\n<p>IS NULL\u662f\u4e00\u500b\u7528\u65bc\u6aa2\u67e5\u67d0\u500b\u6b04\u4f4d\u662f\u5426\u70baNULL\u7684\u689d\u4ef6\u8a9e\u53e5\u3002\u5176\u57fa\u672c\u8a9e\u6cd5\u5982\u4e0b\uff1a<\/p>\n<pre><code>SELECT * FROM \u8868\u540d WHERE \u6b04\u4f4d\u540d IS NULL;<\/code><\/pre>\n<p>\u9019\u689d\u6307\u4ee4\u5c07\u8fd4\u56de\u6240\u6709\u5728\u6307\u5b9a\u6b04\u4f4d\u4e2d\u503c\u70baNULL\u7684\u8a18\u9304\u3002\u4f8b\u5982\uff0c\u5047\u8a2d\u6211\u5011\u6709\u4e00\u500b\u540d\u70ba\u201c\u7528\u6236\u201d\u7684\u8868\u683c\uff0c\u4e26\u4e14\u6211\u5011\u60f3\u67e5\u8a62\u6240\u6709\u6c92\u6709\u63d0\u4f9b\u96fb\u5b50\u90f5\u4ef6\u5730\u5740\u7684\u7528\u6236\uff0c\u6211\u5011\u53ef\u4ee5\u9019\u6a23\u5beb\uff1a<\/p>\n<pre><code>SELECT * FROM \u7528\u6236 WHERE \u96fb\u5b50\u90f5\u4ef6 IS NULL;<\/code><\/pre>\n<h2 id=\"is-not-null%e7%9a%84%e7%94%a8%e6%b3%95-GaERDoziVV\">IS NOT NULL\u7684\u7528\u6cd5<\/h2>\n<p>\u9664\u4e86IS NULL\uff0cMySQL\u9084\u63d0\u4f9b\u4e86IS NOT NULL\u6307\u4ee4\uff0c\u7528\u65bc\u6aa2\u67e5\u67d0\u500b\u6b04\u4f4d\u662f\u5426\u4e0d\u70baNULL\u3002\u5176\u8a9e\u6cd5\u5982\u4e0b\uff1a<\/p>\n<pre><code>SELECT * FROM \u8868\u540d WHERE \u6b04\u4f4d\u540d IS NOT NULL;<\/code><\/pre>\n<p>\u9019\u689d\u6307\u4ee4\u5c07\u8fd4\u56de\u6240\u6709\u5728\u6307\u5b9a\u6b04\u4f4d\u4e2d\u503c\u4e0d\u70baNULL\u7684\u8a18\u9304\u3002\u4f8b\u5982\uff0c\u5982\u679c\u6211\u5011\u60f3\u67e5\u8a62\u6240\u6709\u63d0\u4f9b\u4e86\u96fb\u5b50\u90f5\u4ef6\u5730\u5740\u7684\u7528\u6236\uff0c\u53ef\u4ee5\u9019\u6a23\u5beb\uff1a<\/p>\n<pre><code>SELECT * FROM \u7528\u6236 WHERE \u96fb\u5b50\u90f5\u4ef6 IS NOT NULL;<\/code><\/pre>\n<h2 id=\"is-null%e7%9a%84%e5%af%a6%e9%9a%9b%e6%87%89%e7%94%a8-GaERDoziVV\">IS NULL\u7684\u5be6\u969b\u61c9\u7528<\/h2>\n<p>\u5728\u5be6\u969b\u61c9\u7528\u4e2d\uff0cIS NULL\u6307\u4ee4\u53ef\u4ee5\u7528\u65bc\u591a\u7a2e\u60c5\u5883\u3002\u4f8b\u5982\uff0c\u5728\u6578\u64da\u6e05\u7406\u904e\u7a0b\u4e2d\uff0c\u6211\u5011\u53ef\u80fd\u9700\u8981\u627e\u51fa\u7f3a\u5931\u7684\u6578\u64da\uff0c\u4ee5\u4fbf\u9032\u884c\u88dc\u5168\u6216\u522a\u9664\u3002\u4ee5\u4e0b\u662f\u4e00\u4e9b\u5e38\u898b\u7684\u61c9\u7528\u5834\u666f\uff1a<\/p>\n<ul>\n<li><strong>\u6578\u64da\u5b8c\u6574\u6027\u6aa2\u67e5\uff1a<\/strong>\u5728\u9032\u884c\u6578\u64da\u5206\u6790\u4e4b\u524d\uff0c\u78ba\u4fdd\u6578\u64da\u7684\u5b8c\u6574\u6027\u662f\u975e\u5e38\u91cd\u8981\u7684\u3002\u4f7f\u7528IS NULL\u53ef\u4ee5\u5e6b\u52a9\u6211\u5011\u8b58\u5225\u7f3a\u5931\u7684\u6578\u64da\u3002<\/li>\n<li><strong>\u5831\u544a\u751f\u6210\uff1a<\/strong>\u5728\u751f\u6210\u5831\u544a\u6642\uff0c\u53ef\u80fd\u9700\u8981\u6392\u9664\u67d0\u4e9b\u7f3a\u5931\u6578\u64da\u7684\u8a18\u9304\uff0c\u4ee5\u78ba\u4fdd\u5831\u544a\u7684\u6e96\u78ba\u6027\u3002<\/li>\n<li><strong>\u6578\u64da\u9077\u79fb\uff1a<\/strong>\u5728\u5c07\u6578\u64da\u5f9e\u4e00\u500b\u7cfb\u7d71\u9077\u79fb\u5230\u53e6\u4e00\u500b\u7cfb\u7d71\u6642\uff0c\u6aa2\u67e5NULL\u503c\u53ef\u4ee5\u5e6b\u52a9\u6211\u5011\u78ba\u4fdd\u6578\u64da\u7684\u6b63\u78ba\u6027\u3002<\/li>\n<\/ul>\n<h2 id=\"%e6%b3%a8%e6%84%8f%e4%ba%8b%e9%a0%85-GaERDoziVV\">\u6ce8\u610f\u4e8b\u9805<\/h2>\n<p>\u5728\u4f7f\u7528IS NULL\u6642\uff0c\u6709\u5e7e\u9ede\u9700\u8981\u6ce8\u610f\uff1a<\/p>\n<ul>\n<li>NULL\u4e0d\u7b49\u65bc\u7a7a\u5b57\u7b26\u4e32\u62160\uff0c\u9019\u662f\u9700\u8981\u7279\u5225\u6ce8\u610f\u7684\u5730\u65b9\u3002<\/li>\n<li>\u5728\u9032\u884c\u6bd4\u8f03\u6642\uff0cNULL\u503c\u4e0d\u6703\u88ab\u8a08\u5165\u8a08\u7b97\uff0c\u56e0\u6b64\u5728\u9032\u884c\u805a\u5408\u51fd\u6578\uff08\u5982COUNT\u3001SUM\u7b49\uff09\u6642\uff0cNULL\u503c\u6703\u88ab\u81ea\u52d5\u5ffd\u7565\u3002<\/li>\n<li>\u5728\u4f7f\u7528WHERE\u5b50\u53e5\u6642\uff0c\u5fc5\u9808\u4f7f\u7528IS NULL\u6216IS NOT NULL\u4f86\u6aa2\u67e5NULL\u503c\uff0c\u4e0d\u80fd\u4f7f\u7528\u7b49\u865f\uff08=\uff09\u6216\u4e0d\u7b49\u865f\uff08\uff09\u3002<\/li>\n<\/ul>\n<h2 id=\"%e7%b8%bd%e7%b5%90-GaERDoziVV\">\u7e3d\u7d50<\/h2>\n<p>IS NULL\u6307\u4ee4\u5728MySQL\u4e2d\u662f\u4e00\u500b\u975e\u5e38\u91cd\u8981\u7684\u5de5\u5177\uff0c\u80fd\u5920\u5e6b\u52a9\u958b\u767c\u8005\u548c\u6578\u64da\u5206\u6790\u5e2b\u6709\u6548\u5730\u8655\u7406\u548c\u67e5\u8a62\u7a7a\u503c\u3002\u4e86\u89e3\u5982\u4f55\u4f7f\u7528IS NULL\u548cIS NOT NULL\u53ef\u4ee5\u63d0\u9ad8\u6578\u64da\u67e5\u8a62\u7684\u6e96\u78ba\u6027\u548c\u6548\u7387\u3002\u5728\u9078\u64c7\u5408\u9069\u7684\u6578\u64da\u5eab\u89e3\u6c7a\u65b9\u6848\u6642\uff0c\u8003\u616e\u4f7f\u7528<a href=\"https:\/\/server.hk\">\u9999\u6e2fVPS<\/a>\u4f86\u642d\u5efa\u60a8\u7684MySQL\u74b0\u5883\uff0c\u5c07\u6709\u52a9\u65bc\u63d0\u5347\u60a8\u7684\u6578\u64da\u7ba1\u7406\u80fd\u529b\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u4e86\u89e3MySQL\u6307\u4ee4IS NULL\uff0c\u5b78\u7fd2\u5982\u4f55\u6aa2\u67e5\u8cc7\u6599\u5eab\u4e2d\u6b04\u4f4d\u662f\u5426\u70ba\u7a7a\uff0c\u63d0\u5347\u67e5\u8a62\u6548\u7387\u8207\u6578\u64da\u7ba1\u7406\u80fd\u529b\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-78774","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/78774","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=78774"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/78774\/revisions"}],"predecessor-version":[{"id":78775,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/78774\/revisions\/78775"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=78774"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=78774"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=78774"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}