{"id":175481,"date":"2024-11-08T06:14:17","date_gmt":"2024-11-07T22:14:17","guid":{"rendered":"https:\/\/server.hk\/cnblog\/175481\/"},"modified":"2024-11-08T06:14:18","modified_gmt":"2024-11-07T22:14:18","slug":"%e5%a6%82%e4%bd%95%e4%bd%bf%e7%94%a8%e6%95%b8%e6%93%9a%e5%ba%abcount%e5%87%bd%e6%95%b8%e5%8e%bb%e6%8e%89%e9%87%8d%e8%a4%87%e8%a8%98%e9%8c%84%ef%bc%9f-%e6%95%b8%e6%93%9a%e5%ba%abcount%e5%8e%bb","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/175481\/","title":{"rendered":"\u5982\u4f55\u4f7f\u7528\u6578\u64da\u5eabcount\u51fd\u6578\u53bb\u6389\u91cd\u8907\u8a18\u9304\uff1f (\u6578\u64da\u5eabcount\u53bb\u6389\u91cd\u8907)"},"content":{"rendered":"<h1 id=\"%e5%a6%82%e4%bd%95%e4%bd%bf%e7%94%a8%e6%95%b8%e6%93%9a%e5%ba%abcount%e5%87%bd%e6%95%b8%e5%8e%bb%e6%8e%89%e9%87%8d%e8%a4%87%e8%a8%98%e9%8c%84%ef%bc%9f-%e6%95%b8%e6%93%9a%e5%ba%abcount%e5%8e%bb-cskvPndsSo\">\u5982\u4f55\u4f7f\u7528\u6578\u64da\u5eabcount\u51fd\u6578\u53bb\u6389\u91cd\u8907\u8a18\u9304\uff1f (\u6578\u64da\u5eabcount\u53bb\u6389\u91cd\u8907)<\/h1>\n<p>\u5728\u6578\u64da\u5eab\u7ba1\u7406\u4e2d\uff0c\u91cd\u8907\u8a18\u9304\u662f\u4e00\u500b\u5e38\u898b\u7684\u554f\u984c\uff0c\u7279\u5225\u662f\u5728\u8655\u7406\u5927\u91cf\u6578\u64da\u6642\u3002\u70ba\u4e86\u78ba\u4fdd\u6578\u64da\u7684\u6e96\u78ba\u6027\u548c\u5b8c\u6574\u6027\uff0c\u53bb\u9664\u91cd\u8907\u8a18\u9304\u662f\u5fc5\u8981\u7684\u6b65\u9a5f\u4e4b\u4e00\u3002\u672c\u6587\u5c07\u63a2\u8a0e\u5982\u4f55\u4f7f\u7528\u6578\u64da\u5eab\u4e2d\u7684 <code>COUNT<\/code> \u51fd\u6578\u4f86\u8b58\u5225\u548c\u53bb\u6389\u91cd\u8907\u8a18\u9304\uff0c\u4e26\u63d0\u4f9b\u4e00\u4e9b\u5be6\u7528\u7684\u793a\u4f8b\u548c\u4ee3\u78bc\u7247\u6bb5\u3002<\/p>\n<h2 id=\"%e4%bb%80%e9%ba%bc%e6%98%afcount%e5%87%bd%e6%95%b8%ef%bc%9f-cskvPndsSo\">\u4ec0\u9ebc\u662fCOUNT\u51fd\u6578\uff1f<\/h2>\n<p><code>COUNT<\/code> \u51fd\u6578\u662f SQL \u4e2d\u7684\u4e00\u500b\u805a\u5408\u51fd\u6578\uff0c\u7528\u65bc\u8a08\u7b97\u67e5\u8a62\u7d50\u679c\u4e2d\u884c\u7684\u6578\u91cf\u3002\u5b83\u53ef\u4ee5\u7528\u4f86\u8a08\u7b97\u7279\u5b9a\u5217\u7684\u975e\u7a7a\u503c\u6578\u91cf\uff0c\u6216\u8a08\u7b97\u6574\u500b\u8868\u4e2d\u7684\u884c\u6578\u3002\u9019\u4f7f\u5f97 <code>COUNT<\/code> \u51fd\u6578\u5728\u6578\u64da\u5206\u6790\u548c\u5831\u544a\u4e2d\u975e\u5e38\u6709\u7528\u3002<\/p>\n<h2 id=\"%e8%ad%98%e5%88%a5%e9%87%8d%e8%a4%87%e8%a8%98%e9%8c%84-cskvPndsSo\">\u8b58\u5225\u91cd\u8907\u8a18\u9304<\/h2>\n<p>\u5728\u4f7f\u7528 <code>COUNT<\/code> \u51fd\u6578\u53bb\u6389\u91cd\u8907\u8a18\u9304\u4e4b\u524d\uff0c\u9996\u5148\u9700\u8981\u8b58\u5225\u54ea\u4e9b\u8a18\u9304\u662f\u91cd\u8907\u7684\u3002\u901a\u5e38\uff0c\u6211\u5011\u6703\u6839\u64da\u4e00\u500b\u6216\u591a\u500b\u5217\u7684\u503c\u4f86\u5224\u65b7\u91cd\u8907\u3002\u4f8b\u5982\uff0c\u5047\u8a2d\u6211\u5011\u6709\u4e00\u500b\u540d\u70ba <code>customers<\/code> \u7684\u8868\uff0c\u5305\u542b\u4ee5\u4e0b\u5217\uff1a<\/p>\n<ul>\n<li><code>id<\/code><\/li>\n<li><code>name<\/code><\/li>\n<li><code>email<\/code><\/li>\n<\/ul>\n<p>\u6211\u5011\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b SQL \u67e5\u8a62\u4f86\u8b58\u5225\u91cd\u8907\u7684\u96fb\u5b50\u90f5\u4ef6\u5730\u5740\uff1a<\/p>\n<pre><code>SELECT email, COUNT(*) as count\nFROM customers\nGROUP BY email\nHAVING COUNT(*) &gt; 1;<\/code><\/pre>\n<p>\u9019\u6bb5\u67e5\u8a62\u5c07\u8fd4\u56de\u6240\u6709\u91cd\u8907\u7684\u96fb\u5b50\u90f5\u4ef6\u5730\u5740\u53ca\u5176\u51fa\u73fe\u7684\u6b21\u6578\u3002<\/p>\n<h2 id=\"%e5%8e%bb%e6%8e%89%e9%87%8d%e8%a4%87%e8%a8%98%e9%8c%84-cskvPndsSo\">\u53bb\u6389\u91cd\u8907\u8a18\u9304<\/h2>\n<p>\u4e00\u65e6\u8b58\u5225\u51fa\u91cd\u8907\u8a18\u9304\uff0c\u6211\u5011\u53ef\u4ee5\u4f7f\u7528\u4e0d\u540c\u7684\u65b9\u6cd5\u4f86\u53bb\u6389\u5b83\u5011\u3002\u4ee5\u4e0b\u662f\u5e7e\u7a2e\u5e38\u898b\u7684\u65b9\u6cd5\uff1a<\/p>\n<h3 id=\"%e6%96%b9%e6%b3%95%e4%b8%80%ef%bc%9a%e4%bd%bf%e7%94%a8%e5%ad%90%e6%9f%a5%e8%a9%a2-cskvPndsSo\">\u65b9\u6cd5\u4e00\uff1a\u4f7f\u7528\u5b50\u67e5\u8a62<\/h3>\n<p>\u6211\u5011\u53ef\u4ee5\u4f7f\u7528\u5b50\u67e5\u8a62\u4f86\u522a\u9664\u91cd\u8907\u7684\u8a18\u9304\u3002\u4ee5\u4e0b\u662f\u793a\u4f8b SQL \u67e5\u8a62\uff1a<\/p>\n<pre><code>DELETE FROM customers\nWHERE id NOT IN (\n    SELECT MIN(id)\n    FROM customers\n    GROUP BY email\n);<\/code><\/pre>\n<p>\u9019\u6bb5\u67e5\u8a62\u5c07\u4fdd\u7559\u6bcf\u500b\u96fb\u5b50\u90f5\u4ef6\u5730\u5740\u7684\u7b2c\u4e00\u689d\u8a18\u9304\uff0c\u4e26\u522a\u9664\u5176\u9918\u7684\u91cd\u8907\u8a18\u9304\u3002<\/p>\n<h3 id=\"%e6%96%b9%e6%b3%95%e4%ba%8c%ef%bc%9a%e4%bd%bf%e7%94%a8cte%ef%bc%88%e5%85%ac%e7%94%a8%e8%a1%a8%e8%a1%a8%e9%81%94%e5%bc%8f%ef%bc%89-cskvPndsSo\">\u65b9\u6cd5\u4e8c\uff1a\u4f7f\u7528CTE\uff08\u516c\u7528\u8868\u8868\u9054\u5f0f\uff09<\/h3>\n<p>\u53e6\u4e00\u7a2e\u65b9\u6cd5\u662f\u4f7f\u7528 CTE \u4f86\u522a\u9664\u91cd\u8907\u8a18\u9304\u3002\u4ee5\u4e0b\u662f\u793a\u4f8b\uff1a<\/p>\n<pre><code>WITH CTE AS (\n    SELECT id, email,\n           ROW_NUMBER() OVER (PARTITION BY email ORDER BY id) as row_num\n    FROM customers\n)\nDELETE FROM CTE\nWHERE row_num &gt; 1;<\/code><\/pre>\n<p>\u9019\u6bb5\u67e5\u8a62\u5c07\u70ba\u6bcf\u500b\u96fb\u5b50\u90f5\u4ef6\u5730\u5740\u5206\u914d\u4e00\u500b\u884c\u865f\uff0c\u7136\u5f8c\u522a\u9664\u884c\u865f\u5927\u65bc 1 \u7684\u8a18\u9304\u3002<\/p>\n<h2 id=\"%e7%b8%bd%e7%b5%90-cskvPndsSo\">\u7e3d\u7d50<\/h2>\n<p>\u4f7f\u7528 <code>COUNT<\/code> \u51fd\u6578\u4f86\u8b58\u5225\u548c\u53bb\u6389\u91cd\u8907\u8a18\u9304\u662f\u4e00\u500b\u6709\u6548\u7684\u6578\u64da\u7ba1\u7406\u7b56\u7565\u3002\u901a\u904e\u9069\u7576\u7684 SQL \u67e5\u8a62\uff0c\u6211\u5011\u53ef\u4ee5\u8f15\u9b06\u5730\u627e\u5230\u91cd\u8907\u7684\u6578\u64da\u4e26\u9032\u884c\u6e05\u7406\uff0c\u5f9e\u800c\u63d0\u9ad8\u6578\u64da\u7684\u8cea\u91cf\u548c\u53ef\u9760\u6027\u3002\u5c0d\u65bc\u9700\u8981\u8655\u7406\u5927\u91cf\u6578\u64da\u7684\u4f01\u696d\u4f86\u8aaa\uff0c\u9019\u4e00\u904e\u7a0b\u5c24\u70ba\u91cd\u8981\u3002<\/p>\n<p>\u5982\u679c\u60a8\u6b63\u5728\u5c0b\u627e\u9ad8\u6548\u7684\u6578\u64da\u5eab\u89e3\u6c7a\u65b9\u6848\uff0c\u8003\u616e\u4f7f\u7528 <a href=\"https:\/\/server.hk\">\u9999\u6e2fVPS<\/a> \u4f86\u652f\u6301\u60a8\u7684\u696d\u52d9\u9700\u6c42\u3002\u7121\u8ad6\u662f\u6578\u64da\u5b58\u5132\u9084\u662f\u61c9\u7528\u7a0b\u5e8f\u6258\u7ba1\uff0c<a href=\"https:\/\/server.hk\">\u9999\u6e2f\u4f3a\u670d\u5668<\/a> \u90fd\u80fd\u63d0\u4f9b\u7a69\u5b9a\u7684\u6027\u80fd\u548c\u5b89\u5168\u6027\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u4e86\u89e3\u5982\u4f55\u4f7f\u7528\u6578\u64da\u5eab\u7684COUNT\u51fd\u6578\u53bb\u6389\u91cd\u8907\u8a18\u9304\uff0c\u63d0\u5347\u6578\u64da\u67e5\u8a62\u6548\u7387\uff0c\u78ba\u4fdd\u7d50\u679c\u7684\u6e96\u78ba\u6027\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-175481","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/175481","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=175481"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/175481\/revisions"}],"predecessor-version":[{"id":175482,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/175481\/revisions\/175482"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=175481"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=175481"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=175481"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}