{"id":177535,"date":"2024-11-08T14:57:26","date_gmt":"2024-11-08T06:57:26","guid":{"rendered":"https:\/\/server.hk\/cnblog\/177535\/"},"modified":"2024-11-08T14:57:27","modified_gmt":"2024-11-08T06:57:27","slug":"%e5%a6%82%e4%bd%95%e4%bf%ae%e5%be%a9mysql%e9%8c%af%e8%aa%a41138-sqlstate-42000%ef%bc%88er_invalid_use_of_null%ef%bc%89%e7%84%a1%e6%95%88%e4%bd%bf%e7%94%a8null%e5%80%bc","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/177535\/","title":{"rendered":"\u5982\u4f55\u4fee\u5fa9MySQL\u932f\u8aa41138 &#8211; SQLSTATE: 42000\uff08ER_INVALID_USE_OF_NULL\uff09\u7121\u6548\u4f7f\u7528NULL\u503c"},"content":{"rendered":"<h1 id=\"%e5%a6%82%e4%bd%95%e4%bf%ae%e5%be%a9mysql%e9%8c%af%e8%aa%a41138-sqlstate-42000%ef%bc%88er_invalid_use_of_null%ef%bc%89%e7%84%a1%e6%95%88%e4%bd%bf%e7%94%a8null%e5%80%bc-vxJnOqzHYJ\">\u5982\u4f55\u4fee\u5fa9MySQL\u932f\u8aa41138 &#8211; SQLSTATE: 42000\uff08ER_INVALID_USE_OF_NULL\uff09\u7121\u6548\u4f7f\u7528NULL\u503c<\/h1>\n<p>\u5728\u4f7f\u7528MySQL\u6578\u64da\u5eab\u6642\uff0c\u958b\u767c\u8005\u53ef\u80fd\u6703\u9047\u5230\u5404\u7a2e\u932f\u8aa4\uff0c\u5176\u4e2d\u4e4b\u4e00\u5c31\u662f\u932f\u8aa41138\uff0c\u8a72\u932f\u8aa4\u7684SQLSTATE\u4ee3\u78bc\u70ba42000\uff0c\u8868\u793a\u7121\u6548\u4f7f\u7528NULL\u503c\u3002\u9019\u500b\u932f\u8aa4\u901a\u5e38\u767c\u751f\u5728\u5617\u8a66\u5c07NULL\u503c\u63d2\u5165\u5230\u4e0d\u5141\u8a31NULL\u7684\u5217\u4e2d\uff0c\u6216\u8005\u5728\u67e5\u8a62\u4e2d\u4e0d\u6b63\u78ba\u5730\u4f7f\u7528NULL\u503c\u3002\u672c\u6587\u5c07\u63a2\u8a0e\u8a72\u932f\u8aa4\u7684\u539f\u56e0\u53ca\u5176\u89e3\u6c7a\u65b9\u6848\u3002<\/p>\n<h2 id=\"%e9%8c%af%e8%aa%a4%e5%8e%9f%e5%9b%a0-vxJnOqzHYJ\">\u932f\u8aa4\u539f\u56e0<\/h2>\n<p>MySQL\u932f\u8aa41138\u7684\u4e3b\u8981\u539f\u56e0\u662f\u5c0dNULL\u503c\u7684\u932f\u8aa4\u4f7f\u7528\u3002\u4ee5\u4e0b\u662f\u4e00\u4e9b\u5e38\u898b\u7684\u60c5\u6cc1\uff1a<\/p>\n<ul>\n<li><strong>\u4e0d\u5141\u8a31NULL\u7684\u5217\uff1a<\/strong>\u5982\u679c\u4e00\u500b\u5217\u88ab\u5b9a\u7fa9\u70baNOT NULL\uff0c\u5247\u4e0d\u80fd\u63d2\u5165NULL\u503c\u3002\u4f8b\u5982\uff1a<\/li>\n<pre><code>CREATE TABLE users (\n        id INT NOT NULL AUTO_INCREMENT,\n        username VARCHAR(50) NOT NULL,\n        email VARCHAR(100) NOT NULL,\n        PRIMARY KEY (id)\n    );<\/code><\/pre>\n<p>\u5728\u9019\u500b\u4f8b\u5b50\u4e2d\uff0cusername\u548cemail\u5217\u90fd\u4e0d\u5141\u8a31NULL\u503c\u3002\u5982\u679c\u5617\u8a66\u63d2\u5165\u4e00\u500bNULL\u503c\uff0c\u5c07\u6703\u5f15\u767c\u932f\u8aa41138\u3002<\/p>\n<li><strong>\u4e0d\u6b63\u78ba\u7684\u67e5\u8a62\u8a9e\u6cd5\uff1a<\/strong>\u5728\u67d0\u4e9b\u60c5\u6cc1\u4e0b\uff0c\u67e5\u8a62\u8a9e\u6cd5\u4e0d\u6b63\u78ba\u4e5f\u6703\u5c0e\u81f4\u6b64\u932f\u8aa4\u3002\u4f8b\u5982\uff0c\u4f7f\u7528NULL\u9032\u884c\u6bd4\u8f03\u6642\uff0c\u61c9\u4f7f\u7528IS NULL\u800c\u4e0d\u662f= NULL\u3002<\/li>\n<pre><code>SELECT * FROM users WHERE username = NULL;<\/code><\/pre>\n<p>\u9019\u6a23\u7684\u67e5\u8a62\u5c07\u4e0d\u6703\u8fd4\u56de\u4efb\u4f55\u7d50\u679c\uff0c\u4e26\u53ef\u80fd\u5c0e\u81f4\u932f\u8aa4\u3002<\/p>\n<li><strong>\u4f7f\u7528NULL\u4f5c\u70ba\u51fd\u6578\u53c3\u6578\uff1a<\/strong>\u67d0\u4e9bMySQL\u51fd\u6578\u4e0d\u63a5\u53d7NULL\u4f5c\u70ba\u53c3\u6578\uff0c\u9019\u4e5f\u53ef\u80fd\u5c0e\u81f4\u932f\u8aa4\u3002\u4f8b\u5982\uff0c\u4f7f\u7528NULL\u4f5c\u70baGROUP BY\u6216ORDER BY\u7684\u53c3\u6578\u3002<\/li>\n<\/ul>\n<h2 id=\"%e8%a7%a3%e6%b1%ba%e6%96%b9%e6%a1%88-vxJnOqzHYJ\">\u89e3\u6c7a\u65b9\u6848<\/h2>\n<p>\u8981\u4fee\u5fa9MySQL\u932f\u8aa41138\uff0c\u958b\u767c\u8005\u53ef\u4ee5\u63a1\u53d6\u4ee5\u4e0b\u5e7e\u500b\u6b65\u9a5f\uff1a<\/p>\n<h3 id=\"1-%e6%aa%a2%e6%9f%a5%e8%a1%a8%e7%b5%90%e6%a7%8b-vxJnOqzHYJ\">1. \u6aa2\u67e5\u8868\u7d50\u69cb<\/h3>\n<p>\u9996\u5148\uff0c\u6aa2\u67e5\u8868\u7684\u7d50\u69cb\uff0c\u78ba\u4fdd\u5c0d\u65bc\u4e0d\u5141\u8a31NULL\u7684\u5217\uff0c\u63d2\u5165\u7684\u6578\u64da\u4e0d\u5305\u542bNULL\u503c\u3002\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0bSQL\u8a9e\u53e5\u67e5\u770b\u8868\u7d50\u69cb\uff1a<\/p>\n<pre><code>DESCRIBE users;<\/code><\/pre>\n<h3 id=\"2-%e4%bf%ae%e6%94%b9%e6%8f%92%e5%85%a5%e8%aa%9e%e5%8f%a5-vxJnOqzHYJ\">2. \u4fee\u6539\u63d2\u5165\u8a9e\u53e5<\/h3>\n<p>\u5728\u63d2\u5165\u6578\u64da\u6642\uff0c\u78ba\u4fdd\u63d0\u4f9b\u6240\u6709\u5fc5\u9700\u7684\u975eNULL\u503c\u3002\u4f8b\u5982\uff1a<\/p>\n<pre><code>INSERT INTO users (username, email) VALUES ('john_doe', 'john@example.com');<\/code><\/pre>\n<h3 id=\"3-%e4%bd%bf%e7%94%a8%e6%ad%a3%e7%a2%ba%e7%9a%84%e6%af%94%e8%bc%83%e9%81%8b%e7%ae%97%e7%ac%a6-vxJnOqzHYJ\">3. \u4f7f\u7528\u6b63\u78ba\u7684\u6bd4\u8f03\u904b\u7b97\u7b26<\/h3>\n<p>\u5728\u67e5\u8a62\u4e2d\u4f7f\u7528NULL\u6642\uff0c\u61c9\u4f7f\u7528IS NULL\u6216IS NOT NULL\u3002\u4f8b\u5982\uff1a<\/p>\n<pre><code>SELECT * FROM users WHERE username IS NULL;<\/code><\/pre>\n<h3 id=\"4-%e6%aa%a2%e6%9f%a5%e5%87%bd%e6%95%b8%e5%8f%83%e6%95%b8-vxJnOqzHYJ\">4. \u6aa2\u67e5\u51fd\u6578\u53c3\u6578<\/h3>\n<p>\u5728\u4f7f\u7528MySQL\u51fd\u6578\u6642\uff0c\u78ba\u4fdd\u4e0d\u50b3\u905eNULL\u503c\u4f5c\u70ba\u53c3\u6578\u3002\u5982\u679c\u9700\u8981\u8655\u7406NULL\u503c\uff0c\u53ef\u4ee5\u4f7f\u7528COALESCE\u51fd\u6578\u4f86\u63d0\u4f9b\u9ed8\u8a8d\u503c\u3002\u4f8b\u5982\uff1a<\/p>\n<pre><code>SELECT COALESCE(username, 'default_user') FROM users;<\/code><\/pre>\n<h2 id=\"%e7%b8%bd%e7%b5%90-vxJnOqzHYJ\">\u7e3d\u7d50<\/h2>\n<p>MySQL\u932f\u8aa41138\uff08SQLSTATE: 42000\uff09\u901a\u5e38\u662f\u7531\u65bc\u4e0d\u6b63\u78ba\u5730\u4f7f\u7528NULL\u503c\u5f15\u8d77\u7684\u3002\u901a\u904e\u6aa2\u67e5\u8868\u7d50\u69cb\u3001\u4fee\u6539\u63d2\u5165\u8a9e\u53e5\u3001\u4f7f\u7528\u6b63\u78ba\u7684\u6bd4\u8f03\u904b\u7b97\u7b26\u4ee5\u53ca\u6aa2\u67e5\u51fd\u6578\u53c3\u6578\uff0c\u53ef\u4ee5\u6709\u6548\u5730\u89e3\u6c7a\u6b64\u554f\u984c\u3002\u5c0d\u65bc\u9700\u8981\u7a69\u5b9a\u548c\u9ad8\u6548\u6578\u64da\u5eab\u7ba1\u7406\u7684\u7528\u6236\uff0c\u9078\u64c7\u5408\u9069\u7684 <a href=\"https:\/\/server.hk\">VPS<\/a> \u65b9\u6848\u662f\u81f3\u95dc\u91cd\u8981\u7684\u3002\u7121\u8ad6\u662f <a href=\"https:\/\/server.hk\">\u9999\u6e2fVPS<\/a> \u9084\u662f\u5176\u4ed6\u985e\u578b\u7684 <a href=\"https:\/\/server.hk\">\u4f3a\u670d\u5668<\/a>\uff0c\u90fd\u80fd\u63d0\u4f9b\u7a69\u5b9a\u7684\u6027\u80fd\u548c\u53ef\u9760\u7684\u652f\u6301\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u4fee\u5fa9MySQL\u932f\u8aa41138\uff08ER_INVALID_USE_OF_NULL\uff09\u7684\u65b9\u6cd5\uff0c\u89e3\u91cb\u7121\u6548\u4f7f\u7528NULL\u503c\u7684\u539f\u56e0\u53ca\u89e3\u6c7a\u65b9\u6848\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-177535","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/177535","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=177535"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/177535\/revisions"}],"predecessor-version":[{"id":177536,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/177535\/revisions\/177536"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=177535"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=177535"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=177535"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}