{"id":60609,"date":"2024-10-13T04:17:15","date_gmt":"2024-10-12T20:17:15","guid":{"rendered":"https:\/\/server.hk\/cnblog\/60609\/"},"modified":"2024-10-13T04:17:15","modified_gmt":"2024-10-12T20:17:15","slug":"db2%e5%88%aa%e9%99%a4%e9%87%8d%e8%a4%87%e6%95%b8%e6%93%9a%e7%9a%84%e5%af%a6%e7%8f%be","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/60609\/","title":{"rendered":"DB2\u522a\u9664\u91cd\u8907\u6578\u64da\u7684\u5be6\u73fe"},"content":{"rendered":"

DB2\u522a\u9664\u91cd\u8907\u6578\u64da\u7684\u5be6\u73fe<\/h1>\n

\u5728\u6578\u64da\u5eab\u7ba1\u7406\u4e2d\uff0c\u91cd\u8907\u6578\u64da\u7684\u5b58\u5728\u6703\u5f71\u97ff\u6578\u64da\u7684\u5b8c\u6574\u6027\u548c\u67e5\u8a62\u6548\u7387\u3002IBM\u7684DB2\u6578\u64da\u5eab\u7cfb\u7d71\u63d0\u4f9b\u4e86\u591a\u7a2e\u65b9\u6cd5\u4f86\u8b58\u5225\u548c\u522a\u9664\u91cd\u8907\u6578\u64da\u3002\u672c\u6587\u5c07\u63a2\u8a0e\u5728DB2\u4e2d\u522a\u9664\u91cd\u8907\u6578\u64da\u7684\u5e7e\u7a2e\u5e38\u898b\u65b9\u6cd5\uff0c\u4e26\u63d0\u4f9b\u76f8\u61c9\u7684\u793a\u4f8b\u4ee3\u78bc\u3002<\/p>\n

\u91cd\u8907\u6578\u64da\u7684\u8b58\u5225<\/h2>\n

\u5728\u522a\u9664\u91cd\u8907\u6578\u64da\u4e4b\u524d\uff0c\u9996\u5148\u9700\u8981\u8b58\u5225\u54ea\u4e9b\u6578\u64da\u662f\u91cd\u8907\u7684\u3002\u901a\u5e38\u53ef\u4ee5\u4f7f\u7528GROUP BY\u8a9e\u53e5\u4f86\u67e5\u627e\u91cd\u8907\u7684\u8a18\u9304\u3002\u4f8b\u5982\uff0c\u5047\u8a2d\u6211\u5011\u6709\u4e00\u500b\u540d\u70ba\u201ccustomers\u201d\u7684\u8868\uff0c\u5176\u4e2d\u5305\u542b\u5ba2\u6236\u7684\u59d3\u540d\u548c\u96fb\u5b50\u90f5\u4ef6\u5730\u5740\uff0c\u6211\u5011\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b\u67e5\u8a62\u4f86\u8b58\u5225\u91cd\u8907\u7684\u96fb\u5b50\u90f5\u4ef6\u5730\u5740\uff1a<\/p>\n

SELECT email, COUNT(*) as count\nFROM customers\nGROUP BY email\nHAVING COUNT(*) > 1;<\/code><\/pre>\n
\u9019\u6bb5\u4ee3\u78bc\u5c07\u8fd4\u56de\u6240\u6709\u91cd\u8907\u7684\u96fb\u5b50\u90f5\u4ef6\u5730\u5740\u53ca\u5176\u51fa\u73fe\u7684\u6b21\u6578\u3002<\/p>\n
\u522a\u9664\u91cd\u8907\u6578\u64da\u7684\u65b9\u6cd5<\/h2>\n
\u5728DB2\u4e2d\uff0c\u6709\u5e7e\u7a2e\u65b9\u6cd5\u53ef\u4ee5\u522a\u9664\u91cd\u8907\u6578\u64da\u3002\u4ee5\u4e0b\u662f\u5e7e\u7a2e\u5e38\u898b\u7684\u65b9\u6cd5\uff1a<\/p>\n
\u65b9\u6cd5\u4e00\uff1a\u4f7f\u7528CTE\uff08\u516c\u7528\u8868\u8868\u9054\u5f0f\uff09<\/h3>\n
CTE\u662f\u4e00\u7a2e\u5f37\u5927\u7684\u5de5\u5177\uff0c\u53ef\u4ee5\u5e6b\u52a9\u6211\u5011\u5728\u522a\u9664\u91cd\u8907\u6578\u64da\u6642\u4fdd\u6301\u4ee3\u78bc\u7684\u53ef\u8b80\u6027\u3002\u4ee5\u4e0b\u662f\u4f7f\u7528CTE\u522a\u9664\u91cd\u8907\u6578\u64da\u7684\u793a\u4f8b\uff1a<\/p>\n
WITH CTE AS (\n    SELECT ROW_NUMBER() OVER (PARTITION BY email ORDER BY id) as row_num\n    FROM customers\n)\nDELETE FROM CTE WHERE row_num > 1;<\/code><\/pre>\n
\u5728\u9019\u500b\u793a\u4f8b\u4e2d\uff0c\u6211\u5011\u4f7f\u7528ROW_NUMBER()\u51fd\u6578\u70ba\u6bcf\u500b\u91cd\u8907\u7684\u96fb\u5b50\u90f5\u4ef6\u5730\u5740\u5206\u914d\u4e00\u500b\u884c\u865f\uff0c\u7136\u5f8c\u522a\u9664\u884c\u865f\u5927\u65bc1\u7684\u8a18\u9304\u3002<\/p>\n
\u65b9\u6cd5\u4e8c\uff1a\u4f7f\u7528JOIN\u8a9e\u53e5<\/h3>\n
\u53e6\u4e00\u7a2e\u522a\u9664\u91cd\u8907\u6578\u64da\u7684\u65b9\u6cd5\u662f\u4f7f\u7528JOIN\u8a9e\u53e5\u3002\u4ee5\u4e0b\u662f\u76f8\u61c9\u7684\u793a\u4f8b\uff1a<\/p>\n
DELETE FROM customers\nWHERE id NOT IN (\n    SELECT MIN(id)\n    FROM customers\n    GROUP BY email\n);<\/code><\/pre>\n
\u9019\u6bb5\u4ee3\u78bc\u5c07\u522a\u9664\u6240\u6709\u91cd\u8907\u7684\u96fb\u5b50\u90f5\u4ef6\u5730\u5740\uff0c\u53ea\u4fdd\u7559\u6bcf\u7d44\u91cd\u8907\u8a18\u9304\u4e2did\u6700\u5c0f\u7684\u90a3\u4e00\u689d\u3002<\/p>\n
\u65b9\u6cd5\u4e09\uff1a\u4f7f\u7528DISTINCT\u548cINSERT INTO<\/h3>\n
\u5982\u679c\u60a8\u5e0c\u671b\u4fdd\u7559\u539f\u59cb\u8868\u4e2d\u7684\u552f\u4e00\u8a18\u9304\uff0c\u53ef\u4ee5\u8003\u616e\u5275\u5efa\u4e00\u500b\u65b0\u8868\uff0c\u7136\u5f8c\u5c07\u552f\u4e00\u8a18\u9304\u63d2\u5165\u65b0\u8868\u4e2d\u3002\u4ee5\u4e0b\u662f\u793a\u4f8b\uff1a<\/p>\n
CREATE TABLE unique_customers AS\nSELECT DISTINCT *\nFROM customers;<\/code><\/pre>\n
\u9019\u6a23\uff0c\u60a8\u5c07\u64c1\u6709\u4e00\u500b\u540d\u70ba\u201cunique_customers\u201d\u7684\u65b0\u8868\uff0c\u5176\u4e2d\u53ea\u5305\u542b\u552f\u4e00\u7684\u5ba2\u6236\u8a18\u9304\u3002<\/p>\n
\u6ce8\u610f\u4e8b\u9805<\/h2>\n
\u5728\u522a\u9664\u91cd\u8907\u6578\u64da\u4e4b\u524d\uff0c\u5efa\u8b70\u5148\u5099\u4efd\u6578\u64da\u5eab\uff0c\u4ee5\u9632\u6b62\u610f\u5916\u522a\u9664\u91cd\u8981\u6578\u64da\u3002\u6b64\u5916\uff0c\u61c9\u4ed4\u7d30\u6aa2\u67e5\u522a\u9664\u689d\u4ef6\uff0c\u4ee5\u78ba\u4fdd\u4e0d\u6703\u522a\u9664\u6240\u9700\u7684\u6578\u64da\u3002<\/p>\n
\u7e3d\u7d50<\/h2>\n
\u5728DB2\u4e2d\u522a\u9664\u91cd\u8907\u6578\u64da\u662f\u4e00\u500b\u91cd\u8981\u7684\u6578\u64da\u7ba1\u7406\u4efb\u52d9\uff0c\u53ef\u4ee5\u901a\u904e\u591a\u7a2e\u65b9\u6cd5\u5be6\u73fe\uff0c\u5305\u62ec\u4f7f\u7528CTE\u3001JOIN\u8a9e\u53e5\u548cDISTINCT\u3002\u9019\u4e9b\u65b9\u6cd5\u5404\u6709\u512a\u7f3a\u9ede\uff0c\u9078\u64c7\u5408\u9069\u7684\u65b9\u6cd5\u53d6\u6c7a\u65bc\u5177\u9ad4\u7684\u9700\u6c42\u548c\u6578\u64da\u7d50\u69cb\u3002\u5c0d\u65bc\u9700\u8981\u9ad8\u6548\u6578\u64da\u7ba1\u7406\u7684\u4f01\u696d\uff0c\u9078\u64c7\u5408\u9069\u7684\u6578\u64da\u5eab\u89e3\u6c7a\u65b9\u6848\u81f3\u95dc\u91cd\u8981\u3002\u82e5\u60a8\u5c0d\u65bc\u9999\u6e2fVPS<\/a><\/code>\u6216\u4e91\u670d\u52a1\u5668<\/a><\/code>\u6709\u8208\u8da3\uff0c\u8acb\u8a2a\u554f\u6211\u5011\u7684\u7db2\u7ad9\u4ee5\u7372\u53d6\u66f4\u591a\u4fe1\u606f\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
\u63a2\u7d22DB2\u4e2d\u522a\u9664\u91cd\u8907\u6578\u64da\u7684\u6709\u6548\u65b9\u6cd5\uff0c\u63d0\u5347\u6578\u64da\u8cea\u91cf\uff0c\u512a\u5316\u6578\u64da\u5eab\u6027\u80fd\uff0c\u78ba\u4fdd\u6578\u64da\u7684\u552f\u4e00\u6027\u548c\u6e96\u78ba\u6027\u3002<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[101],"tags":[],"class_list":["post-60609","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/60609","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"}],"author":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/comments?post=60609"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/60609\/revisions"}],"predecessor-version":[{"id":60610,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/60609\/revisions\/60610"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=60609"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=60609"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=60609"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}