{"id":160733,"date":"2024-11-04T00:33:22","date_gmt":"2024-11-03T16:33:22","guid":{"rendered":"https:\/\/server.hk\/cnblog\/160733\/"},"modified":"2024-11-04T00:33:23","modified_gmt":"2024-11-03T16:33:23","slug":"%e8%b3%87%e6%96%99%e5%ba%ab%e6%95%99%e7%a8%8b%ef%bc%9amysql-is-null%ef%bc%9a%e7%a9%ba%e5%80%bc%e6%9f%a5%e8%a9%a2","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/160733\/","title":{"rendered":"\u8cc7\u6599\u5eab\u6559\u7a0b\uff1aMySQL IS NULL\uff1a\u7a7a\u503c\u67e5\u8a62"},"content":{"rendered":"<h1 id=\"%e8%b3%87%e6%96%99%e5%ba%ab%e6%95%99%e7%a8%8b%ef%bc%9amysql-is-null%ef%bc%9a%e7%a9%ba%e5%80%bc%e6%9f%a5%e8%a9%a2-URlwptmFAW\">\u8cc7\u6599\u5eab\u6559\u7a0b\uff1aMySQL IS NULL\uff1a\u7a7a\u503c\u67e5\u8a62<\/h1>\n<p>\u5728\u8cc7\u6599\u5eab\u7ba1\u7406\u4e2d\uff0c\u8655\u7406\u7a7a\u503c\uff08NULL\uff09\u662f\u4e00\u500b\u91cd\u8981\u7684\u8ab2\u984c\u3002MySQL\u4f5c\u70ba\u4e00\u500b\u6d41\u884c\u7684\u95dc\u806f\u5f0f\u8cc7\u6599\u5eab\u7ba1\u7406\u7cfb\u7d71\uff0c\u63d0\u4f9b\u4e86\u591a\u7a2e\u65b9\u6cd5\u4f86\u67e5\u8a62\u548c\u8655\u7406\u7a7a\u503c\u3002\u672c\u6587\u5c07\u6df1\u5165\u63a2\u8a0e\u5982\u4f55\u4f7f\u7528MySQL\u7684IS NULL\u8a9e\u53e5\u4f86\u9032\u884c\u7a7a\u503c\u67e5\u8a62\uff0c\u4e26\u63d0\u4f9b\u76f8\u95dc\u7684\u7bc4\u4f8b\u548c\u6700\u4f73\u5be6\u8e10\u3002<\/p>\n<h2 id=\"%e4%bb%80%e9%ba%bc%e6%98%afnull%ef%bc%9f-URlwptmFAW\">\u4ec0\u9ebc\u662fNULL\uff1f<\/h2>\n<p>\u5728MySQL\u4e2d\uff0cNULL\u662f\u4e00\u500b\u7279\u6b8a\u7684\u6a19\u8a18\uff0c\u7528\u4f86\u8868\u793a\u7f3a\u5931\u6216\u672a\u77e5\u7684\u6578\u64da\u3002NULL\u4e26\u4e0d\u7b49\u540c\u65bc\u96f6\uff080\uff09\u6216\u7a7a\u5b57\u7b26\u4e32\uff08&#8221;&#8221;\uff09\uff0c\u800c\u662f\u8868\u793a\u4e00\u500b\u4e0d\u5b58\u5728\u7684\u503c\u3002\u9019\u610f\u5473\u8457\u5728\u9032\u884c\u6578\u64da\u67e5\u8a62\u6642\uff0cNULL\u503c\u9700\u8981\u7279\u5225\u8655\u7406\u3002<\/p>\n<h2 id=\"%e4%bd%bf%e7%94%a8is-null%e9%80%b2%e8%a1%8c%e6%9f%a5%e8%a9%a2-URlwptmFAW\">\u4f7f\u7528IS NULL\u9032\u884c\u67e5\u8a62<\/h2>\n<p>\u8981\u67e5\u8a62\u67d0\u500b\u6b04\u4f4d\u662f\u5426\u70baNULL\uff0c\u53ef\u4ee5\u4f7f\u7528IS NULL\u8a9e\u53e5\u3002\u9019\u662f\u4e00\u500b\u975e\u5e38\u7c21\u55ae\u4e14\u6709\u6548\u7684\u67e5\u8a62\u65b9\u5f0f\u3002\u4ee5\u4e0b\u662f\u57fa\u672c\u7684\u8a9e\u6cd5\uff1a<\/p>\n<pre><code>SELECT * FROM \u8868\u540d WHERE \u6b04\u4f4d\u540d IS NULL;<\/code><\/pre>\n<p>\u9019\u689d\u67e5\u8a62\u5c07\u8fd4\u56de\u6240\u6709\u5728\u6307\u5b9a\u6b04\u4f4d\u4e2d\u503c\u70baNULL\u7684\u8a18\u9304\u3002<\/p>\n<h3 id=\"%e7%af%84%e4%be%8b-URlwptmFAW\">\u7bc4\u4f8b<\/h3>\n<p>\u5047\u8a2d\u6211\u5011\u6709\u4e00\u500b\u540d\u70ba\u201cusers\u201d\u7684\u8868\uff0c\u7d50\u69cb\u5982\u4e0b\uff1a<\/p>\n<pre><code>CREATE TABLE users (\n    id INT AUTO_INCREMENT PRIMARY KEY,\n    name VARCHAR(100),\n    email VARCHAR(100),\n    phone VARCHAR(15) NULL\n);<\/code><\/pre>\n<p>\u5728\u9019\u500b\u8868\u4e2d\uff0cphone\u6b04\u4f4d\u53ef\u4ee5\u70baNULL\u3002\u82e5\u8981\u67e5\u8a62\u6240\u6709\u6c92\u6709\u63d0\u4f9b\u96fb\u8a71\u865f\u78bc\u7684\u7528\u6236\uff0c\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b\u67e5\u8a62\uff1a<\/p>\n<pre><code>SELECT * FROM users WHERE phone IS NULL;<\/code><\/pre>\n<p>\u9019\u5c07\u8fd4\u56de\u6240\u6709phone\u6b04\u4f4d\u70baNULL\u7684\u7528\u6236\u8a18\u9304\u3002<\/p>\n<h2 id=\"%e4%bd%bf%e7%94%a8is-not-null%e9%80%b2%e8%a1%8c%e6%9f%a5%e8%a9%a2-URlwptmFAW\">\u4f7f\u7528IS NOT NULL\u9032\u884c\u67e5\u8a62<\/h2>\n<p>\u9664\u4e86\u67e5\u8a62NULL\u503c\u5916\uff0c\u6709\u6642\u5019\u6211\u5011\u4e5f\u9700\u8981\u67e5\u8a62\u975eNULL\u503c\u3002\u9019\u6642\u53ef\u4ee5\u4f7f\u7528IS NOT NULL\u8a9e\u53e5\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\u67e5\u8a62\u5c07\u8fd4\u56de\u6240\u6709\u5728\u6307\u5b9a\u6b04\u4f4d\u4e2d\u503c\u4e0d\u70baNULL\u7684\u8a18\u9304\u3002<\/p>\n<h3 id=\"%e7%af%84%e4%be%8b-URlwptmFAW\">\u7bc4\u4f8b<\/h3>\n<p>\u7e7c\u7e8c\u4f7f\u7528\u201cusers\u201d\u8868\u7684\u4f8b\u5b50\uff0c\u82e5\u8981\u67e5\u8a62\u6240\u6709\u63d0\u4f9b\u96fb\u8a71\u865f\u78bc\u7684\u7528\u6236\uff0c\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b\u67e5\u8a62\uff1a<\/p>\n<pre><code>SELECT * FROM users WHERE phone IS NOT NULL;<\/code><\/pre>\n<p>\u9019\u5c07\u8fd4\u56de\u6240\u6709phone\u6b04\u4f4d\u4e0d\u70baNULL\u7684\u7528\u6236\u8a18\u9304\u3002<\/p>\n<h2 id=\"null%e7%9a%84%e6%af%94%e8%bc%83%e8%88%87%e6%b3%a8%e6%84%8f%e4%ba%8b%e9%a0%85-URlwptmFAW\">NULL\u7684\u6bd4\u8f03\u8207\u6ce8\u610f\u4e8b\u9805<\/h2>\n<p>\u5728MySQL\u4e2d\uff0cNULL\u7684\u6bd4\u8f03\u9700\u8981\u7279\u5225\u6ce8\u610f\u3002\u4f7f\u7528\u7b49\u865f\uff08=\uff09\u6216\u4e0d\u7b49\u865f\uff08\uff09\u4f86\u6bd4\u8f03NULL\u503c\u5c07\u4e0d\u6703\u8fd4\u56de\u9810\u671f\u7684\u7d50\u679c\u3002\u4f8b\u5982\uff1a<\/p>\n<pre><code>SELECT * FROM users WHERE phone = NULL;<\/code><\/pre>\n<p>\u9019\u689d\u67e5\u8a62\u4e0d\u6703\u8fd4\u56de\u4efb\u4f55\u7d50\u679c\uff0c\u56e0\u70baNULL\u7121\u6cd5\u8207\u4efb\u4f55\u503c\u9032\u884c\u6bd4\u8f03\u3002\u6b63\u78ba\u7684\u505a\u6cd5\u662f\u4f7f\u7528IS NULL\u6216IS NOT NULL\u3002<\/p>\n<h2 id=\"%e6%9c%80%e4%bd%b3%e5%af%a6%e8%b8%90-URlwptmFAW\">\u6700\u4f73\u5be6\u8e10<\/h2>\n<ul>\n<li>\u5728\u8a2d\u8a08\u8cc7\u6599\u5eab\u6642\uff0c\u8003\u616e\u54ea\u4e9b\u6b04\u4f4d\u53ef\u4ee5\u70baNULL\uff0c\u4e26\u6839\u64da\u696d\u52d9\u9700\u6c42\u9032\u884c\u8a2d\u8a08\u3002<\/li>\n<li>\u5728\u67e5\u8a62\u6642\uff0c\u59cb\u7d42\u4f7f\u7528IS NULL\u6216IS NOT NULL\u4f86\u8655\u7406\u7a7a\u503c\u3002<\/li>\n<li>\u5b9a\u671f\u6aa2\u67e5\u8cc7\u6599\u5eab\u4e2d\u7684NULL\u503c\uff0c\u4ee5\u78ba\u4fdd\u6578\u64da\u7684\u5b8c\u6574\u6027\u548c\u6e96\u78ba\u6027\u3002<\/li>\n<\/ul>\n<h2 id=\"%e7%b8%bd%e7%b5%90-URlwptmFAW\">\u7e3d\u7d50<\/h2>\n<p>\u5728MySQL\u4e2d\uff0c\u6b63\u78ba\u8655\u7406NULL\u503c\u5c0d\u65bc\u7dad\u8b77\u8cc7\u6599\u5eab\u7684\u5b8c\u6574\u6027\u81f3\u95dc\u91cd\u8981\u3002\u4f7f\u7528IS NULL\u548cIS NOT NULL\u8a9e\u53e5\u53ef\u4ee5\u6709\u6548\u5730\u67e5\u8a62\u7a7a\u503c\u548c\u975e\u7a7a\u503c\uff0c\u5e6b\u52a9\u958b\u767c\u8005\u66f4\u597d\u5730\u7ba1\u7406\u6578\u64da\u3002\u4e86\u89e3NULL\u7684\u7279\u6027\u53ca\u5176\u5728\u67e5\u8a62\u4e2d\u7684\u61c9\u7528\uff0c\u5c07\u6709\u52a9\u65bc\u63d0\u9ad8\u8cc7\u6599\u5eab\u64cd\u4f5c\u7684\u6548\u7387\u548c\u6e96\u78ba\u6027\u3002<\/p>\n<p>\u5982\u679c\u60a8\u6b63\u5728\u5c0b\u627e\u9ad8\u6548\u7684 <a href=\"https:\/\/server.hk\">VPS<\/a> \u89e3\u6c7a\u65b9\u6848\uff0cServer.HK \u63d0\u4f9b\u591a\u7a2e\u9078\u64c7\uff0c\u9069\u5408\u5404\u7a2e\u9700\u6c42\u3002\u7121\u8ad6\u662f <a href=\"https:\/\/server.hk\">\u9999\u6e2fVPS<\/a> \u9084\u662f\u5176\u4ed6\u670d\u52d9\uff0c\u6211\u5011\u90fd\u80fd\u70ba\u60a8\u63d0\u4f9b\u652f\u6301\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u5b78\u7fd2\u5982\u4f55\u5728MySQL\u4e2d\u4f7f\u7528IS NULL\u9032\u884c\u7a7a\u503c\u67e5\u8a62\uff0c\u638c\u63e1\u8cc7\u6599\u5eab\u64cd\u4f5c\u7684\u95dc\u9375\u6280\u5de7\uff0c\u63d0\u5347\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-160733","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/160733","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=160733"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/160733\/revisions"}],"predecessor-version":[{"id":160734,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/160733\/revisions\/160734"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=160733"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=160733"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=160733"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}