{"id":175275,"date":"2024-11-08T04:30:19","date_gmt":"2024-11-07T20:30:19","guid":{"rendered":"https:\/\/server.hk\/cnblog\/175275\/"},"modified":"2024-11-08T04:30:20","modified_gmt":"2024-11-07T20:30:20","slug":"%e5%a6%82%e4%bd%95%e4%bd%bf%e7%94%a8mysql%e9%80%b2%e8%a1%8c%e9%ab%98%e6%95%88%e7%9a%84%e6%95%b8%e6%93%9a%e5%ba%ab%e5%8e%bb%e9%87%8d%e6%93%8d%e4%bd%9c%ef%bc%9f-%e6%95%b8%e6%93%9a%e5%ba%ab%e5%8e%bb","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/175275\/","title":{"rendered":"\u5982\u4f55\u4f7f\u7528MySQL\u9032\u884c\u9ad8\u6548\u7684\u6578\u64da\u5eab\u53bb\u91cd\u64cd\u4f5c\uff1f (\u6578\u64da\u5eab\u53bb\u91cd mysql)"},"content":{"rendered":"

\u5982\u4f55\u4f7f\u7528MySQL\u9032\u884c\u9ad8\u6548\u7684\u6578\u64da\u5eab\u53bb\u91cd\u64cd\u4f5c\uff1f<\/h1>\n

\u5728\u6578\u64da\u5eab\u7ba1\u7406\u4e2d\uff0c\u6578\u64da\u53bb\u91cd\u662f\u4e00\u500b\u91cd\u8981\u7684\u904e\u7a0b\uff0c\u7279\u5225\u662f\u5728\u8655\u7406\u5927\u91cf\u6578\u64da\u6642\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\u5982\u4f55\u5728MySQL\u4e2d\u9ad8\u6548\u5730\u9032\u884c\u6578\u64da\u5eab\u53bb\u91cd\u64cd\u4f5c\uff0c\u4e26\u63d0\u4f9b\u4e00\u4e9b\u5be6\u7528\u7684\u793a\u4f8b\u548c\u4ee3\u78bc\u7247\u6bb5\u3002<\/p>\n

\u70ba\u4ec0\u9ebc\u9700\u8981\u6578\u64da\u53bb\u91cd\uff1f<\/h2>\n

\u6578\u64da\u53bb\u91cd\u7684\u4e3b\u8981\u76ee\u7684\u662f\u6d88\u9664\u91cd\u8907\u6578\u64da\uff0c\u9019\u4e0d\u50c5\u53ef\u4ee5\u7bc0\u7701\u5b58\u5132\u7a7a\u9593\uff0c\u9084\u80fd\u63d0\u9ad8\u67e5\u8a62\u6548\u7387\u3002\u91cd\u8907\u6578\u64da\u53ef\u80fd\u6703\u5c0e\u81f4\u6578\u64da\u4e0d\u4e00\u81f4\u6027\uff0c\u5f71\u97ff\u5831\u544a\u548c\u5206\u6790\u7684\u6e96\u78ba\u6027\u3002\u56e0\u6b64\uff0c\u5b9a\u671f\u9032\u884c\u6578\u64da\u53bb\u91cd\u662f\u6578\u64da\u7ba1\u7406\u7684\u91cd\u8981\u7d44\u6210\u90e8\u5206\u3002<\/p>\n

MySQL\u4e2d\u7684\u6578\u64da\u53bb\u91cd\u65b9\u6cd5<\/h2>\n

1. \u4f7f\u7528DISTINCT\u95dc\u9375\u5b57<\/h3>\n

\u5728\u67e5\u8a62\u4e2d\u4f7f\u7528DISTINCT\u95dc\u9375\u5b57\u53ef\u4ee5\u8f15\u9b06\u5730\u7372\u53d6\u552f\u4e00\u7684\u6578\u64da\u884c\u3002\u4f8b\u5982\uff0c\u5047\u8a2d\u6211\u5011\u6709\u4e00\u500b\u540d\u70ba\u201ccustomers\u201d\u7684\u8868\uff0c\u4e26\u5e0c\u671b\u7372\u53d6\u552f\u4e00\u7684\u57ce\u5e02\u5217\u8868\uff1a<\/p>\n

SELECT DISTINCT city FROM customers;<\/code><\/pre>\n
\u9019\u689d\u67e5\u8a62\u5c07\u8fd4\u56de\u201ccustomers\u201d\u8868\u4e2d\u6240\u6709\u4e0d\u540c\u7684\u57ce\u5e02\u540d\u7a31\u3002<\/p>\n
2. \u4f7f\u7528GROUP BY\u5b50\u53e5<\/h3>\n
\u53e6\u4e00\u7a2e\u53bb\u91cd\u7684\u65b9\u6cd5\u662f\u4f7f\u7528GROUP BY\u5b50\u53e5\u3002\u9019\u4e0d\u50c5\u53ef\u4ee5\u53bb\u9664\u91cd\u8907\u6578\u64da\uff0c\u9084\u53ef\u4ee5\u9032\u884c\u805a\u5408\u64cd\u4f5c\u3002\u4f8b\u5982\uff0c\u82e5\u8981\u8a08\u7b97\u6bcf\u500b\u57ce\u5e02\u7684\u5ba2\u6236\u6578\u91cf\uff0c\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b\u67e5\u8a62\uff1a<\/p>\n
SELECT city, COUNT(*) as customer_count FROM customers GROUP BY city;<\/code><\/pre>\n
\u9019\u5c07\u8fd4\u56de\u6bcf\u500b\u57ce\u5e02\u53ca\u5176\u5c0d\u61c9\u7684\u5ba2\u6236\u6578\u91cf\u3002<\/p>\n
3. \u4f7f\u7528UNIQUE\u7d04\u675f<\/h3>\n
\u5728\u5275\u5efa\u8868\u6642\uff0c\u53ef\u4ee5\u4f7f\u7528UNIQUE\u7d04\u675f\u4f86\u9632\u6b62\u63d2\u5165\u91cd\u8907\u6578\u64da\u3002\u4f8b\u5982\uff1a<\/p>\n
CREATE TABLE users (\n    id INT AUTO_INCREMENT PRIMARY KEY,\n    email VARCHAR(255) UNIQUE\n);<\/code><\/pre>\n
\u9019\u6a23\uff0c\u4efb\u4f55\u5617\u8a66\u63d2\u5165\u91cd\u8907\u96fb\u5b50\u90f5\u4ef6\u7684\u64cd\u4f5c\u90fd\u6703\u5931\u6557\uff0c\u5f9e\u800c\u4fdd\u6301\u6578\u64da\u7684\u552f\u4e00\u6027\u3002<\/p>\n
4. \u4f7f\u7528DELETE\u8a9e\u53e5\u53bb\u9664\u91cd\u8907\u6578\u64da<\/h3>\n
\u5982\u679c\u6578\u64da\u5eab\u4e2d\u5df2\u7d93\u5b58\u5728\u91cd\u8907\u6578\u64da\uff0c\u53ef\u4ee5\u4f7f\u7528DELETE\u8a9e\u53e5\u4f86\u522a\u9664\u5b83\u5011\u3002\u4ee5\u4e0b\u662f\u4e00\u500b\u793a\u4f8b\uff0c\u5047\u8a2d\u6211\u5011\u8981\u522a\u9664\u201ccustomers\u201d\u8868\u4e2d\u91cd\u8907\u7684\u8a18\u9304\uff1a<\/p>\n
DELETE c1 FROM customers c1\nINNER JOIN customers c2 \nWHERE \n    c1.id > c2.id AND \n    c1.email = c2.email;<\/code><\/pre>\n
\u9019\u689d\u67e5\u8a62\u5c07\u522a\u9664\u201ccustomers\u201d\u8868\u4e2d\u6240\u6709\u91cd\u8907\u7684\u96fb\u5b50\u90f5\u4ef6\u8a18\u9304\uff0c\u53ea\u4fdd\u7559\u6bcf\u7d44\u91cd\u8907\u8a18\u9304\u4e2d\u7684\u4e00\u500b\u3002<\/p>\n
5. \u4f7f\u7528CTE\uff08\u516c\u7528\u8868\u8868\u9054\u5f0f\uff09<\/h3>\n
\u5728MySQL 8.0\u53ca\u4ee5\u4e0a\u7248\u672c\u4e2d\uff0c\u53ef\u4ee5\u4f7f\u7528\u516c\u7528\u8868\u8868\u9054\u5f0f\uff08CTE\uff09\u4f86\u9032\u884c\u66f4\u8907\u96dc\u7684\u53bb\u91cd\u64cd\u4f5c\u3002\u4f8b\u5982\uff1a<\/p>\n
WITH cte AS (\n    SELECT *, ROW_NUMBER() OVER (PARTITION BY email ORDER BY id) as rn\n    FROM customers\n)\nDELETE FROM cte WHERE rn > 1;<\/code><\/pre>\n
\u9019\u5c07\u522a\u9664\u6240\u6709\u91cd\u8907\u7684\u96fb\u5b50\u90f5\u4ef6\uff0c\u53ea\u4fdd\u7559\u6bcf\u7d44\u4e2d\u7684\u7b2c\u4e00\u500b\u3002<\/p>\n
\u7e3d\u7d50<\/h2>\n
\u5728MySQL\u4e2d\u9032\u884c\u6578\u64da\u53bb\u91cd\u64cd\u4f5c\u6709\u591a\u7a2e\u65b9\u6cd5\uff0c\u5305\u62ec\u4f7f\u7528DISTINCT\u3001GROUP BY\u3001UNIQUE\u7d04\u675f\u3001DELETE\u8a9e\u53e5\u4ee5\u53caCTE\u7b49\u3002\u9078\u64c7\u5408\u9069\u7684\u65b9\u6cd5\u53d6\u6c7a\u65bc\u5177\u9ad4\u7684\u9700\u6c42\u548c\u6578\u64da\u7d50\u69cb\u3002\u5b9a\u671f\u9032\u884c\u6578\u64da\u53bb\u91cd\u4e0d\u50c5\u80fd\u63d0\u9ad8\u6578\u64da\u5eab\u7684\u6027\u80fd\uff0c\u9084\u80fd\u78ba\u4fdd\u6578\u64da\u7684\u6e96\u78ba\u6027\u548c\u4e00\u81f4\u6027\u3002<\/p>\n
\u5982\u679c\u60a8\u6b63\u5728\u5c0b\u627e\u9ad8\u6548\u7684\u6578\u64da\u5eab\u89e3\u6c7a\u65b9\u6848\uff0c\u8003\u616e\u4f7f\u7528\u9999\u6e2fVPS<\/a>\u4f86\u6258\u7ba1\u60a8\u7684MySQL\u6578\u64da\u5eab\uff0c\u9019\u5c07\u70ba\u60a8\u7684\u696d\u52d9\u63d0\u4f9b\u7a69\u5b9a\u548c\u53ef\u9760\u7684\u652f\u6301\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
\u5b78\u7fd2\u5982\u4f55\u4f7f\u7528MySQL\u9032\u884c\u9ad8\u6548\u7684\u6578\u64da\u5eab\u53bb\u91cd\u64cd\u4f5c\uff0c\u63d0\u5347\u6578\u64da\u8cea\u91cf\uff0c\u512a\u5316\u67e5\u8a62\u6027\u80fd\uff0c\u7c21\u5316\u6578\u64da\u7ba1\u7406\u6d41\u7a0b\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-175275","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/175275","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=175275"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/175275\/revisions"}],"predecessor-version":[{"id":175276,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/175275\/revisions\/175276"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=175275"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=175275"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=175275"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}