{"id":169015,"date":"2024-11-06T18:10:16","date_gmt":"2024-11-06T10:10:16","guid":{"rendered":"https:\/\/server.hk\/cnblog\/169015\/"},"modified":"2024-11-06T18:10:17","modified_gmt":"2024-11-06T10:10:17","slug":"%e9%9d%a2%e8%a9%a6%e7%aa%81%e6%93%8a%ef%bc%9amysql-%e4%b8%ad%e5%a6%82%e4%bd%95%e5%8e%bb%e9%87%8d%ef%bc%9f","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/169015\/","title":{"rendered":"\u9762\u8a66\u7a81\u64ca\uff1aMySQL \u4e2d\u5982\u4f55\u53bb\u91cd\uff1f"},"content":{"rendered":"<h1 id=\"%e9%9d%a2%e8%a9%a6%e7%aa%81%e6%93%8a%ef%bc%9amysql-%e4%b8%ad%e5%a6%82%e4%bd%95%e5%8e%bb%e9%87%8d%ef%bc%9f-RwxTGiWgOa\">\u9762\u8a66\u7a81\u64ca\uff1aMySQL \u4e2d\u5982\u4f55\u53bb\u91cd\uff1f<\/h1>\n<p>\u5728\u6578\u64da\u5eab\u7ba1\u7406\u4e2d\uff0c\u91cd\u8907\u6578\u64da\u7684\u5b58\u5728\u53ef\u80fd\u6703\u5c0e\u81f4\u67e5\u8a62\u7d50\u679c\u4e0d\u6e96\u78ba\uff0c\u5f71\u97ff\u6578\u64da\u5206\u6790\u7684\u7d50\u679c\u3002\u56e0\u6b64\uff0c\u5b78\u6703\u5982\u4f55\u5728 MySQL \u4e2d\u53bb\u91cd\u662f\u6bcf\u4f4d\u6578\u64da\u5eab\u7ba1\u7406\u54e1\u548c\u958b\u767c\u8005\u5fc5\u9808\u638c\u63e1\u7684\u6280\u80fd\u4e4b\u4e00\u3002\u672c\u6587\u5c07\u6df1\u5165\u63a2\u8a0e MySQL \u4e2d\u7684\u53bb\u91cd\u65b9\u6cd5\uff0c\u5e6b\u52a9\u8b80\u8005\u5728\u9762\u8a66\u4e2d\u812b\u7a4e\u800c\u51fa\u3002<\/p>\n<h2 id=\"%e7%82%ba%e4%bb%80%e9%ba%bc%e9%9c%80%e8%a6%81%e5%8e%bb%e9%87%8d%ef%bc%9f-RwxTGiWgOa\">\u70ba\u4ec0\u9ebc\u9700\u8981\u53bb\u91cd\uff1f<\/h2>\n<p>\u5728\u6578\u64da\u5eab\u4e2d\uff0c\u91cd\u8907\u7684\u6578\u64da\u4e0d\u50c5\u6703\u6d6a\u8cbb\u5b58\u5132\u7a7a\u9593\uff0c\u9084\u53ef\u80fd\u5c0e\u81f4\u6578\u64da\u4e0d\u4e00\u81f4\u6027\u3002\u8209\u4f8b\u4f86\u8aaa\uff0c\u5047\u8a2d\u4e00\u500b\u5ba2\u6236\u7684\u8a02\u55ae\u8a18\u9304\u4e2d\u51fa\u73fe\u4e86\u591a\u6b21\u76f8\u540c\u7684\u8a02\u55ae\uff0c\u9019\u5c07\u4f7f\u5f97\u92b7\u552e\u5831\u544a\u4e0d\u6e96\u78ba\uff0c\u5f71\u97ff\u5546\u696d\u6c7a\u7b56\u3002\u56e0\u6b64\uff0c\u53bb\u91cd\u662f\u78ba\u4fdd\u6578\u64da\u8cea\u91cf\u7684\u91cd\u8981\u6b65\u9a5f\u3002<\/p>\n<h2 id=\"mysql-%e4%b8%ad%e7%9a%84%e5%8e%bb%e9%87%8d%e6%96%b9%e6%b3%95-RwxTGiWgOa\">MySQL \u4e2d\u7684\u53bb\u91cd\u65b9\u6cd5<\/h2>\n<p>\u5728 MySQL \u4e2d\uff0c\u53bb\u91cd\u4e3b\u8981\u53ef\u4ee5\u901a\u904e\u4ee5\u4e0b\u5e7e\u7a2e\u65b9\u6cd5\u5be6\u73fe\uff1a<\/p>\n<h3 id=\"1-%e4%bd%bf%e7%94%a8-distinct-%e9%97%9c%e9%8d%b5%e5%ad%97-RwxTGiWgOa\">1. \u4f7f\u7528 DISTINCT \u95dc\u9375\u5b57<\/h3>\n<p>\u6700\u5e38\u898b\u7684\u53bb\u91cd\u65b9\u6cd5\u662f\u4f7f\u7528 <code>DISTINCT<\/code> \u95dc\u9375\u5b57\u3002\u9019\u500b\u95dc\u9375\u5b57\u53ef\u4ee5\u7528\u65bc <code>SELECT<\/code> \u8a9e\u53e5\u4e2d\uff0c\u5f9e\u800c\u8fd4\u56de\u552f\u4e00\u7684\u8a18\u9304\u3002<\/p>\n<pre><code>SELECT DISTINCT column1, column2 FROM table_name;<\/code><\/pre>\n<p>\u4f8b\u5982\uff0c\u5982\u679c\u6211\u5011\u6709\u4e00\u500b\u540d\u70ba <code>customers<\/code> \u7684\u8868\uff0c\u4e26\u5e0c\u671b\u7372\u53d6\u6240\u6709\u4e0d\u540c\u7684\u57ce\u5e02\uff0c\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b\u67e5\u8a62\uff1a<\/p>\n<pre><code>SELECT DISTINCT city FROM customers;<\/code><\/pre>\n<h3 id=\"2-%e4%bd%bf%e7%94%a8-group-by-%e5%ad%90%e5%8f%a5-RwxTGiWgOa\">2. \u4f7f\u7528 GROUP BY \u5b50\u53e5<\/h3>\n<p>\u53e6\u4e00\u7a2e\u53bb\u91cd\u7684\u65b9\u6cd5\u662f\u4f7f\u7528 <code>GROUP BY<\/code> \u5b50\u53e5\u3002\u9019\u500b\u65b9\u6cd5\u4e0d\u50c5\u53ef\u4ee5\u53bb\u91cd\uff0c\u9084\u53ef\u4ee5\u9032\u884c\u805a\u5408\u8a08\u7b97\u3002<\/p>\n<pre><code>SELECT column1, COUNT(*) FROM table_name GROUP BY column1;<\/code><\/pre>\n<p>\u4f8b\u5982\uff0c\u82e5\u8981\u67e5\u8a62\u6bcf\u500b\u57ce\u5e02\u7684\u5ba2\u6236\u6578\u91cf\uff0c\u53ef\u4ee5\u9019\u6a23\u5beb\uff1a<\/p>\n<pre><code>SELECT city, COUNT(*) FROM customers GROUP BY city;<\/code><\/pre>\n<h3 id=\"3-%e4%bd%bf%e7%94%a8%e5%ad%90%e6%9f%a5%e8%a9%a2-RwxTGiWgOa\">3. \u4f7f\u7528\u5b50\u67e5\u8a62<\/h3>\n<p>\u5728\u67d0\u4e9b\u60c5\u6cc1\u4e0b\uff0c\u4f7f\u7528\u5b50\u67e5\u8a62\u4e5f\u53ef\u4ee5\u9054\u5230\u53bb\u91cd\u7684\u6548\u679c\u3002\u9019\u7a2e\u65b9\u6cd5\u901a\u5e38\u7528\u65bc\u66f4\u8907\u96dc\u7684\u67e5\u8a62\u4e2d\u3002<\/p>\n<pre><code>SELECT * FROM (SELECT DISTINCT column1 FROM table_name) AS temp;<\/code><\/pre>\n<p>\u9019\u6a23\u7684\u67e5\u8a62\u53ef\u4ee5\u5148\u5728\u5b50\u67e5\u8a62\u4e2d\u53bb\u91cd\uff0c\u7136\u5f8c\u518d\u5f9e\u4e2d\u9078\u64c7\u6240\u9700\u7684\u6578\u64da\u3002<\/p>\n<h3 id=\"4-%e4%bd%bf%e7%94%a8-unique-%e7%b4%84%e6%9d%9f-RwxTGiWgOa\">4. \u4f7f\u7528 UNIQUE \u7d04\u675f<\/h3>\n<p>\u5728\u5275\u5efa\u8868\u6642\uff0c\u53ef\u4ee5\u4f7f\u7528 <code>UNIQUE<\/code> \u7d04\u675f\u4f86\u9632\u6b62\u91cd\u8907\u6578\u64da\u7684\u63d2\u5165\u3002\u9019\u6a23\u53ef\u4ee5\u5728\u6578\u64da\u63d2\u5165\u968e\u6bb5\u5c31\u907f\u514d\u91cd\u8907\u7684\u554f\u984c\u3002<\/p>\n<pre><code>CREATE TABLE customers (\n    id INT AUTO_INCREMENT PRIMARY KEY,\n    email VARCHAR(255) UNIQUE\n);<\/code><\/pre>\n<p>\u5728\u9019\u500b\u4f8b\u5b50\u4e2d\uff0c<code>email<\/code> \u6b04\u4f4d\u88ab\u8a2d\u7f6e\u70ba\u552f\u4e00\uff0c\u9019\u6a23\u5728\u63d2\u5165\u6578\u64da\u6642\uff0c\u5982\u679c\u5617\u8a66\u63d2\u5165\u91cd\u8907\u7684\u96fb\u5b50\u90f5\u4ef6\u5730\u5740\uff0c\u5c07\u6703\u5f15\u767c\u932f\u8aa4\u3002<\/p>\n<h2 id=\"%e7%b8%bd%e7%b5%90-RwxTGiWgOa\">\u7e3d\u7d50<\/h2>\n<p>\u5728 MySQL \u4e2d\uff0c\u53bb\u91cd\u662f\u78ba\u4fdd\u6578\u64da\u8cea\u91cf\u7684\u91cd\u8981\u6b65\u9a5f\u3002\u901a\u904e\u4f7f\u7528 <code>DISTINCT<\/code>\u3001<code>GROUP BY<\/code>\u3001\u5b50\u67e5\u8a62\u4ee5\u53ca <code>UNIQUE<\/code> \u7d04\u675f\u7b49\u65b9\u6cd5\uff0c\u958b\u767c\u8005\u53ef\u4ee5\u6709\u6548\u5730\u7ba1\u7406\u548c\u6e05\u7406\u6578\u64da\u3002\u638c\u63e1\u9019\u4e9b\u6280\u5de7\u4e0d\u50c5\u80fd\u63d0\u5347\u6578\u64da\u5eab\u7684\u6027\u80fd\uff0c\u9084\u80fd\u5728\u9762\u8a66\u4e2d\u5c55\u793a\u51fa\u4f60\u7684\u5c08\u696d\u77e5\u8b58\u3002<\/p>\n<p>\u5982\u679c\u4f60\u5c0d\u65bc\u6578\u64da\u5eab\u7ba1\u7406\u6709\u66f4\u6df1\u5165\u7684\u9700\u6c42\uff0c\u8003\u616e\u4f7f\u7528 <a href=\"https:\/\/server.hk\">\u9999\u6e2fVPS<\/a> \u4f86\u642d\u5efa\u4f60\u7684\u6578\u64da\u5eab\u74b0\u5883\uff0c\u4eab\u53d7\u66f4\u9ad8\u6548\u7684\u6578\u64da\u8655\u7406\u80fd\u529b\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u4e86\u89e3 MySQL \u4e2d\u7684\u53bb\u91cd\u6280\u5de7\uff0c\u638c\u63e1\u9762\u8a66\u5fc5\u5099\u7684\u6578\u64da\u8655\u7406\u6280\u80fd\uff0c\u63d0\u5347\u4f60\u7684\u6578\u64da\u5eab\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-169015","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/169015","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=169015"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/169015\/revisions"}],"predecessor-version":[{"id":169016,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/169015\/revisions\/169016"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=169015"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=169015"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=169015"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}