{"id":76310,"date":"2024-10-16T05:36:14","date_gmt":"2024-10-15T21:36:14","guid":{"rendered":"https:\/\/server.hk\/cnblog\/76310\/"},"modified":"2024-10-16T05:36:14","modified_gmt":"2024-10-15T21:36:14","slug":"mysql%e5%af%a6%e7%8f%be%e5%8e%bb%e9%87%8d%e7%9a%84%e6%96%b9%e6%b3%95%e8%88%87%e6%8a%80%e5%b7%a7-%e6%80%8e%e6%a8%a3%e8%ae%93mysql%e6%95%b8%e6%93%9a%e5%ba%ab%e5%8e%bb%e9%87%8d","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/76310\/","title":{"rendered":"MySQL\u5be6\u73fe\u53bb\u91cd\u7684\u65b9\u6cd5\u8207\u6280\u5de7 (\u600e\u6a23\u8b93MySQL\u6578\u64da\u5eab\u53bb\u91cd)"},"content":{"rendered":"<h1 id=\"mysql%e5%af%a6%e7%8f%be%e5%8e%bb%e9%87%8d%e7%9a%84%e6%96%b9%e6%b3%95%e8%88%87%e6%8a%80%e5%b7%a7-%e6%80%8e%e6%a8%a3%e8%ae%93mysql%e6%95%b8%e6%93%9a%e5%ba%ab%e5%8e%bb%e9%87%8d-igyBBXyuUh\">MySQL\u5be6\u73fe\u53bb\u91cd\u7684\u65b9\u6cd5\u8207\u6280\u5de7 (\u600e\u6a23\u8b93MySQL\u6578\u64da\u5eab\u53bb\u91cd)<\/h1>\n<p>\u5728\u6578\u64da\u5eab\u7ba1\u7406\u4e2d\uff0c\u6578\u64da\u7684\u91cd\u8907\u6027\u662f\u4e00\u500b\u5e38\u898b\u7684\u554f\u984c\u3002\u91cd\u8907\u7684\u6578\u64da\u4e0d\u50c5\u6703\u6d6a\u8cbb\u5b58\u5132\u7a7a\u9593\uff0c\u9084\u53ef\u80fd\u5c0e\u81f4\u67e5\u8a62\u7d50\u679c\u7684\u4e0d\u6e96\u78ba\u6027\u3002MySQL\u4f5c\u70ba\u4e00\u500b\u6d41\u884c\u7684\u95dc\u4fc2\u578b\u6578\u64da\u5eab\u7ba1\u7406\u7cfb\u7d71\uff0c\u63d0\u4f9b\u4e86\u591a\u7a2e\u65b9\u6cd5\u4f86\u5be6\u73fe\u6578\u64da\u53bb\u91cd\u3002\u672c\u6587\u5c07\u63a2\u8a0e\u5e7e\u7a2e\u6709\u6548\u7684\u53bb\u91cd\u6280\u5de7\uff0c\u5e6b\u52a9\u7528\u6236\u66f4\u597d\u5730\u7ba1\u7406\u5176\u6578\u64da\u5eab\u3002<\/p>\n<h2 id=\"1-%e4%bd%bf%e7%94%a8-distinct-%e9%97%9c%e9%8d%b5%e5%ad%97-igyBBXyuUh\">1. \u4f7f\u7528 DISTINCT \u95dc\u9375\u5b57<\/h2>\n<p>\u5728\u57f7\u884c\u67e5\u8a62\u6642\uff0c\u6700\u7c21\u55ae\u7684\u53bb\u91cd\u65b9\u6cd5\u662f\u4f7f\u7528 <code>DISTINCT<\/code> \u95dc\u9375\u5b57\u3002\u9019\u500b\u95dc\u9375\u5b57\u53ef\u4ee5\u7528\u65bc\u9078\u64c7\u552f\u4e00\u7684\u6578\u64da\u884c\uff0c\u5f9e\u800c\u904e\u6ffe\u6389\u91cd\u8907\u7684\u8a18\u9304\u3002<\/p>\n<pre><code>SELECT DISTINCT column_name 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\u552f\u4e00\u7684\u57ce\u5e02\u5217\u8868\uff0c\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b\u67e5\u8a62\uff1a<\/p>\n<pre><code>SELECT DISTINCT city FROM customers;<\/code><\/pre>\n<h2 id=\"2-%e4%bd%bf%e7%94%a8-group-by-%e5%ad%90%e5%8f%a5-igyBBXyuUh\">2. \u4f7f\u7528 GROUP BY \u5b50\u53e5<\/h2>\n<p>\u53e6\u4e00\u7a2e\u53bb\u91cd\u7684\u65b9\u6cd5\u662f\u4f7f\u7528 <code>GROUP BY<\/code> \u5b50\u53e5\u3002\u9019\u4e0d\u50c5\u53ef\u4ee5\u53bb\u9664\u91cd\u8907\u7684\u6578\u64da\uff0c\u9084\u53ef\u4ee5\u5c0d\u6578\u64da\u9032\u884c\u805a\u5408\u64cd\u4f5c\u3002<\/p>\n<pre><code>SELECT column_name, COUNT(*) FROM table_name GROUP BY column_name;<\/code><\/pre>\n<p>\u4f8b\u5982\uff0c\u82e5\u8981\u8a08\u7b97\u6bcf\u500b\u57ce\u5e02\u7684\u5ba2\u6236\u6578\u91cf\uff0c\u53ef\u4ee5\u9019\u6a23\u67e5\u8a62\uff1a<\/p>\n<pre><code>SELECT city, COUNT(*) FROM customers GROUP BY city;<\/code><\/pre>\n<h2 id=\"3-%e4%bd%bf%e7%94%a8-unique-%e7%b4%84%e6%9d%9f-igyBBXyuUh\">3. \u4f7f\u7528 UNIQUE \u7d04\u675f<\/h2>\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\uff0c\u7576\u5617\u8a66\u63d2\u5165\u91cd\u8907\u7684\u6578\u64da\u6642\uff0cMySQL\u6703\u8fd4\u56de\u932f\u8aa4\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> \u5217\u88ab\u8a2d\u7f6e\u70ba\u552f\u4e00\uff0c\u9019\u610f\u5473\u8457\u6bcf\u500b\u5ba2\u6236\u7684\u96fb\u5b50\u90f5\u4ef6\u5730\u5740\u5fc5\u9808\u662f\u7368\u4e00\u7121\u4e8c\u7684\u3002<\/p>\n<h2 id=\"4-%e4%bd%bf%e7%94%a8-delete-%e8%aa%9e%e5%8f%a5%e5%8e%bb%e9%99%a4%e9%87%8d%e8%a4%87%e6%95%b8%e6%93%9a-igyBBXyuUh\">4. \u4f7f\u7528 DELETE \u8a9e\u53e5\u53bb\u9664\u91cd\u8907\u6578\u64da<\/h2>\n<p>\u5982\u679c\u6578\u64da\u5eab\u4e2d\u5df2\u7d93\u5b58\u5728\u91cd\u8907\u7684\u8a18\u9304\uff0c\u53ef\u4ee5\u4f7f\u7528 <code>DELETE<\/code> \u8a9e\u53e5\u4f86\u522a\u9664\u9019\u4e9b\u91cd\u8907\u7684\u6578\u64da\u3002\u9019\u901a\u5e38\u9700\u8981\u4e00\u500b\u5b50\u67e5\u8a62\u4f86\u8b58\u5225\u91cd\u8907\u7684\u884c\u3002<\/p>\n<pre><code>DELETE FROM table_name\nWHERE id NOT IN (\n    SELECT MIN(id)\n    FROM table_name\n    GROUP BY column_name\n);<\/code><\/pre>\n<p>\u9019\u6bb5\u4ee3\u78bc\u5c07\u522a\u9664\u6240\u6709\u91cd\u8907\u7684\u884c\uff0c\u53ea\u4fdd\u7559\u6bcf\u7d44\u91cd\u8907\u884c\u4e2d\u7684\u7b2c\u4e00\u500b\u3002<\/p>\n<h2 id=\"5-%e4%bd%bf%e7%94%a8-row_number-%e5%87%bd%e6%95%b8-igyBBXyuUh\">5. \u4f7f\u7528 ROW_NUMBER() \u51fd\u6578<\/h2>\n<p>\u5728 MySQL 8.0 \u53ca\u4ee5\u4e0a\u7248\u672c\u4e2d\uff0c\u53ef\u4ee5\u4f7f\u7528 <code>ROW_NUMBER()<\/code> \u51fd\u6578\u4f86\u6a19\u8a18\u6bcf\u4e00\u884c\uff0c\u7136\u5f8c\u6839\u64da\u9019\u4e9b\u6a19\u8a18\u4f86\u522a\u9664\u91cd\u8907\u7684\u6578\u64da\u3002<\/p>\n<pre><code>WITH cte AS (\n    SELECT *, ROW_NUMBER() OVER (PARTITION BY column_name ORDER BY id) AS rn\n    FROM table_name\n)\nDELETE FROM cte WHERE rn &gt; 1;<\/code><\/pre>\n<p>\u9019\u6bb5\u4ee3\u78bc\u5c07\u522a\u9664\u6240\u6709\u91cd\u8907\u7684\u884c\uff0c\u53ea\u4fdd\u7559\u6bcf\u7d44\u91cd\u8907\u884c\u4e2d\u7684\u7b2c\u4e00\u500b\u3002<\/p>\n<h2 id=\"%e7%b8%bd%e7%b5%90-igyBBXyuUh\">\u7e3d\u7d50<\/h2>\n<p>\u5728 MySQL \u4e2d\uff0c\u53bb\u91cd\u662f\u4e00\u500b\u91cd\u8981\u7684\u6578\u64da\u7ba1\u7406\u4efb\u52d9\u3002\u901a\u904e\u4f7f\u7528 <code>DISTINCT<\/code>\u3001<code>GROUP BY<\/code>\u3001<code>UNIQUE<\/code> \u7d04\u675f\u3001<code>DELETE<\/code> \u8a9e\u53e5\u4ee5\u53ca <code>ROW_NUMBER()<\/code> \u51fd\u6578\uff0c\u4f7f\u7528\u8005\u53ef\u4ee5\u6709\u6548\u5730\u7ba1\u7406\u548c\u6e05\u7406\u5176\u6578\u64da\u5eab\u4e2d\u7684\u91cd\u8907\u6578\u64da\u3002\u9019\u4e0d\u50c5\u80fd\u63d0\u9ad8\u6578\u64da\u7684\u6e96\u78ba\u6027\uff0c\u9084\u80fd\u63d0\u5347\u67e5\u8a62\u6027\u80fd\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\u4f86\u904b\u884c\u60a8\u7684 MySQL \u6578\u64da\u5eab\uff0cServer.HK \u63d0\u4f9b\u4e86\u591a\u7a2e\u9078\u64c7\uff0c\u6eff\u8db3\u4e0d\u540c\u9700\u6c42\u7684\u7528\u6236\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\u7a69\u5b9a\u7684\u652f\u6301\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u63a2\u7d22MySQL\u53bb\u91cd\u7684\u65b9\u6cd5\u8207\u6280\u5de7\uff0c\u5b78\u7fd2\u5982\u4f55\u6709\u6548\u6e05\u7406\u6578\u64da\u5eab\u4e2d\u7684\u91cd\u8907\u6578\u64da\uff0c\u63d0\u5347\u6578\u64da\u8cea\u91cf\u8207\u67e5\u8a62\u6548\u7387\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-76310","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/76310","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=76310"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/76310\/revisions"}],"predecessor-version":[{"id":76311,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/76310\/revisions\/76311"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=76310"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=76310"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=76310"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}