{"id":195171,"date":"2024-11-13T12:48:18","date_gmt":"2024-11-13T04:48:18","guid":{"rendered":"https:\/\/server.hk\/cnblog\/195171\/"},"modified":"2024-11-13T12:48:19","modified_gmt":"2024-11-13T04:48:19","slug":"%e5%84%aa%e5%8c%96%e6%9f%a5%e8%a9%a2%e6%95%88%e7%8e%87%ef%bc%8c%e5%af%a6%e7%8f%be%e6%95%b8%e6%93%9a%e5%ba%ab%e5%a4%9a%e8%a1%a8%e6%9f%a5%e8%a9%a2%e5%8e%bb%e9%87%8d-%e6%95%b8%e6%93%9a%e5%ba%ab%e5%a4%9a","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/195171\/","title":{"rendered":"\u512a\u5316\u67e5\u8a62\u6548\u7387\uff0c\u5be6\u73fe\u6578\u64da\u5eab\u591a\u8868\u67e5\u8a62\u53bb\u91cd (\u6578\u64da\u5eab\u591a\u8868\u67e5\u8a62\u53bb\u91cd)"},"content":{"rendered":"

\u512a\u5316\u67e5\u8a62\u6548\u7387\uff0c\u5be6\u73fe\u6578\u64da\u5eab\u591a\u8868\u67e5\u8a62\u53bb\u91cd<\/h1>\n

\u5728\u7576\u4eca\u6578\u64da\u9a45\u52d5\u7684\u4e16\u754c\u4e2d\uff0c\u6578\u64da\u5eab\u7684\u67e5\u8a62\u6548\u7387\u5c0d\u65bc\u61c9\u7528\u7a0b\u5e8f\u7684\u6027\u80fd\u81f3\u95dc\u91cd\u8981\u3002\u5c24\u5176\u662f\u5728\u6d89\u53ca\u591a\u8868\u67e5\u8a62\u7684\u60c5\u6cc1\u4e0b\uff0c\u5982\u4f55\u6709\u6548\u5730\u53bb\u91cd\u6578\u64da\u6210\u70ba\u4e86\u958b\u767c\u8005\u9762\u81e8\u7684\u4e00\u5927\u6311\u6230\u3002\u672c\u6587\u5c07\u63a2\u8a0e\u5982\u4f55\u512a\u5316\u67e5\u8a62\u6548\u7387\uff0c\u5be6\u73fe\u6578\u64da\u5eab\u591a\u8868\u67e5\u8a62\u7684\u53bb\u91cd\uff0c\u4e26\u63d0\u4f9b\u4e00\u4e9b\u5be6\u7528\u7684\u6280\u5de7\u548c\u793a\u4f8b\u3002<\/p>\n

\u591a\u8868\u67e5\u8a62\u7684\u57fa\u672c\u6982\u5ff5<\/h2>\n

\u591a\u8868\u67e5\u8a62\u662f\u6307\u5728\u4e00\u500b\u67e5\u8a62\u4e2d\u540c\u6642\u5f9e\u591a\u500b\u8868\u4e2d\u6aa2\u7d22\u6578\u64da\u3002\u9019\u901a\u5e38\u6d89\u53ca\u5230\u4f7f\u7528 JOIN \u8a9e\u53e5\u4f86\u9023\u63a5\u4e0d\u540c\u7684\u8868\u3002\u96d6\u7136\u591a\u8868\u67e5\u8a62\u53ef\u4ee5\u63d0\u4f9b\u66f4\u8c50\u5bcc\u7684\u6578\u64da\uff0c\u4f46\u5982\u679c\u4e0d\u52a0\u4ee5\u512a\u5316\uff0c\u53ef\u80fd\u6703\u5c0e\u81f4\u6027\u80fd\u554f\u984c\uff0c\u7279\u5225\u662f\u5728\u6578\u64da\u91cf\u9f90\u5927\u7684\u60c5\u6cc1\u4e0b\u3002<\/p>\n

\u67e5\u8a62\u53bb\u91cd\u7684\u91cd\u8981\u6027<\/h2>\n

\u5728\u591a\u8868\u67e5\u8a62\u4e2d\uff0c\u53bb\u91cd\u662f\u6307\u6d88\u9664\u91cd\u8907\u7684\u6578\u64da\u884c\u3002\u9019\u4e0d\u50c5\u53ef\u4ee5\u6e1b\u5c11\u8fd4\u56de\u7684\u6578\u64da\u91cf\uff0c\u9084\u80fd\u63d0\u9ad8\u67e5\u8a62\u7684\u6548\u7387\u3002\u91cd\u8907\u6578\u64da\u7684\u5b58\u5728\u53ef\u80fd\u6703\u5c0e\u81f4\u4e0d\u5fc5\u8981\u7684\u8a08\u7b97\u548c\u7db2\u7d61\u50b3\u8f38\uff0c\u5f9e\u800c\u5f71\u97ff\u6574\u9ad4\u6027\u80fd\u3002<\/p>\n

\u512a\u5316\u67e5\u8a62\u6548\u7387\u7684\u7b56\u7565<\/h2>\n

1. \u4f7f\u7528 DISTINCT \u95dc\u9375\u5b57<\/h3>\n

\u5728 SQL \u67e5\u8a62\u4e2d\uff0c\u4f7f\u7528 DISTINCT<\/code> \u95dc\u9375\u5b57\u53ef\u4ee5\u5e6b\u52a9\u53bb\u9664\u91cd\u8907\u7684\u6578\u64da\u884c\u3002\u4f8b\u5982\uff1a<\/p>\n

SELECT DISTINCT column1, column2 \nFROM table1 \nJOIN table2 ON table1.id = table2.foreign_id;<\/code><\/pre>\n
\u9019\u6a23\u7684\u67e5\u8a62\u5c07\u53ea\u8fd4\u56de\u552f\u4e00\u7684 column1<\/code> \u548c column2<\/code> \u7d44\u5408\uff0c\u5f9e\u800c\u6e1b\u5c11\u91cd\u8907\u6578\u64da\u7684\u5f71\u97ff\u3002<\/p>\n
2. \u4f7f\u7528 GROUP BY \u8a9e\u53e5<\/h3>\n
\u53e6\u4e00\u7a2e\u53bb\u91cd\u7684\u65b9\u6cd5\u662f\u4f7f\u7528 GROUP BY<\/code> \u8a9e\u53e5\u3002\u9019\u4e0d\u50c5\u53ef\u4ee5\u53bb\u9664\u91cd\u8907\u6578\u64da\uff0c\u9084\u53ef\u4ee5\u9032\u884c\u805a\u5408\u8a08\u7b97\u3002\u4f8b\u5982\uff1a<\/p>\n
SELECT column1, COUNT(*) \nFROM table1 \nJOIN table2 ON table1.id = table2.foreign_id \nGROUP BY column1;<\/code><\/pre>\n
\u9019\u6a23\u7684\u67e5\u8a62\u5c07\u8fd4\u56de\u6bcf\u500b column1<\/code> \u7684\u552f\u4e00\u503c\u53ca\u5176\u51fa\u73fe\u7684\u6b21\u6578\u3002<\/p>\n
3. \u9069\u7576\u4f7f\u7528\u7d22\u5f15<\/h3>\n
\u7d22\u5f15\u53ef\u4ee5\u986f\u8457\u63d0\u9ad8\u67e5\u8a62\u6027\u80fd\u3002\u5c0d\u65bc\u7d93\u5e38\u7528\u65bc\u67e5\u8a62\u7684\u5217\uff0c\u61c9\u8003\u616e\u5275\u5efa\u7d22\u5f15\u3002\u9019\u6a23\u53ef\u4ee5\u52a0\u5feb\u6578\u64da\u6aa2\u7d22\u901f\u5ea6\uff0c\u5f9e\u800c\u63d0\u9ad8\u6574\u9ad4\u67e5\u8a62\u6548\u7387\u3002<\/p>\n
4. \u6e1b\u5c11\u8fd4\u56de\u7684\u5217\u6578<\/h3>\n
\u5728\u67e5\u8a62\u4e2d\uff0c\u53ea\u9078\u64c7\u5fc5\u8981\u7684\u5217\u53ef\u4ee5\u6e1b\u5c11\u6578\u64da\u7684\u50b3\u8f38\u91cf\u3002\u4f8b\u5982\uff0c\u907f\u514d\u4f7f\u7528 SELECT *<\/code>\uff0c\u800c\u662f\u660e\u78ba\u6307\u5b9a\u9700\u8981\u7684\u5217\uff1a<\/p>\n
SELECT column1, column2 \nFROM table1 \nJOIN table2 ON table1.id = table2.foreign_id;<\/code><\/pre>\n
5. \u4f7f\u7528\u5b50\u67e5\u8a62<\/h3>\n
\u5728\u67d0\u4e9b\u60c5\u6cc1\u4e0b\uff0c\u4f7f\u7528\u5b50\u67e5\u8a62\u53ef\u4ee5\u5e6b\u52a9\u7c21\u5316\u67e5\u8a62\u4e26\u53bb\u9664\u91cd\u8907\u6578\u64da\u3002\u4f8b\u5982\uff1a<\/p>\n
SELECT column1 \nFROM (SELECT DISTINCT column1 \n      FROM table1 \n      JOIN table2 ON table1.id = table2.foreign_id) AS subquery;<\/code><\/pre>\n
\u7d50\u8ad6<\/h2>\n
\u512a\u5316\u6578\u64da\u5eab\u7684\u591a\u8868\u67e5\u8a62\u6548\u7387\u548c\u53bb\u91cd\u662f\u63d0\u5347\u61c9\u7528\u6027\u80fd\u7684\u95dc\u9375\u3002\u901a\u904e\u4f7f\u7528 DISTINCT<\/code>\u3001GROUP BY<\/code>\u3001\u9069\u7576\u7684\u7d22\u5f15\u3001\u6e1b\u5c11\u8fd4\u56de\u7684\u5217\u6578\u4ee5\u53ca\u5b50\u67e5\u8a62\u7b49\u6280\u8853\uff0c\u958b\u767c\u8005\u53ef\u4ee5\u6709\u6548\u5730\u63d0\u9ad8\u67e5\u8a62\u6548\u7387\uff0c\u6e1b\u5c11\u91cd\u8907\u6578\u64da\u7684\u5f71\u97ff\u3002<\/p>\n
\u5c0d\u65bc\u9700\u8981\u9ad8\u6548\u6578\u64da\u8655\u7406\u7684\u4f01\u696d\uff0c\u9078\u64c7\u5408\u9069\u7684 VPS<\/a> \u89e3\u6c7a\u65b9\u6848\u81f3\u95dc\u91cd\u8981\u3002\u7121\u8ad6\u662f\u9078\u64c7 \u9999\u6e2fVPS<\/a> \u9084\u662f\u5176\u4ed6\u985e\u578b\u7684 \u4f3a\u670d\u5668<\/a>\uff0c\u90fd\u80fd\u70ba\u60a8\u7684\u6578\u64da\u5eab\u64cd\u4f5c\u63d0\u4f9b\u7a69\u5b9a\u7684\u652f\u6301\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
\u63d0\u5347\u67e5\u8a62\u6548\u7387\uff0c\u5be6\u73fe\u6578\u64da\u5eab\u591a\u8868\u67e5\u8a62\u53bb\u91cd\uff0c\u78ba\u4fdd\u6578\u64da\u6e96\u78ba\u6027\u8207\u6027\u80fd\uff0c\u512a\u5316\u6578\u64da\u8655\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-195171","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/195171","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=195171"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/195171\/revisions"}],"predecessor-version":[{"id":195172,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/195171\/revisions\/195172"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=195171"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=195171"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=195171"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}