{"id":174969,"date":"2024-11-08T01:17:19","date_gmt":"2024-11-07T17:17:19","guid":{"rendered":"https:\/\/server.hk\/cnblog\/174969\/"},"modified":"2024-11-08T01:17:20","modified_gmt":"2024-11-07T17:17:20","slug":"%e5%a6%82%e4%bd%95%e8%ae%93-join-%e8%b7%91%e5%be%97%e6%9b%b4%e5%bf%ab%ef%bc%9f","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/174969\/","title":{"rendered":"\u5982\u4f55\u8b93 JOIN \u8dd1\u5f97\u66f4\u5feb\uff1f"},"content":{"rendered":"

\u5982\u4f55\u8b93 JOIN \u8dd1\u5f97\u66f4\u5feb\uff1f<\/h1>\n

\u5728\u8cc7\u6599\u5eab\u7ba1\u7406\u7cfb\u7d71\u4e2d\uff0cJOIN \u662f\u4e00\u500b\u975e\u5e38\u91cd\u8981\u7684\u64cd\u4f5c\uff0c\u901a\u5e38\u7528\u65bc\u5f9e\u591a\u500b\u8868\u4e2d\u6aa2\u7d22\u76f8\u95dc\u6578\u64da\u3002\u7136\u800c\uff0c\u7576\u6578\u64da\u91cf\u589e\u5927\u6642\uff0cJOIN \u64cd\u4f5c\u53ef\u80fd\u6703\u8b8a\u5f97\u975e\u5e38\u7de9\u6162\uff0c\u5f71\u97ff\u6574\u9ad4\u6027\u80fd\u3002\u672c\u6587\u5c07\u63a2\u8a0e\u4e00\u4e9b\u512a\u5316 JOIN \u64cd\u4f5c\u7684\u6280\u5de7\uff0c\u5e6b\u52a9\u958b\u767c\u8005\u63d0\u9ad8\u67e5\u8a62\u6548\u7387\u3002<\/p>\n

1. \u4f7f\u7528\u9069\u7576\u7684\u7d22\u5f15<\/h2>\n

\u7d22\u5f15\u662f\u63d0\u9ad8\u67e5\u8a62\u6027\u80fd\u7684\u95dc\u9375\u3002\u5c0d\u65bc\u6d89\u53ca JOIN \u7684\u67e5\u8a62\uff0c\u78ba\u4fdd\u5728 JOIN \u7684\u6b04\u4f4d\u4e0a\u5efa\u7acb\u7d22\u5f15\uff0c\u53ef\u4ee5\u986f\u8457\u63d0\u9ad8\u67e5\u8a62\u901f\u5ea6\u3002\u4f8b\u5982\uff0c\u5047\u8a2d\u6709\u5169\u500b\u8868\uff1ausers<\/code> \u548c orders<\/code>\uff0c\u5982\u679c\u6211\u5011\u7d93\u5e38\u6839\u64da user_id<\/code> \u4f86\u9032\u884c JOIN\uff0c\u5247\u61c9\u5728\u9019\u5169\u500b\u8868\u7684 user_id<\/code> \u6b04\u4f4d\u4e0a\u5efa\u7acb\u7d22\u5f15\u3002<\/p>\n

CREATE INDEX idx_user_id ON users(user_id);\nCREATE INDEX idx_user_id ON orders(user_id);\n<\/code><\/pre>\n
2. \u907f\u514d SELECT *<\/h2>\n
\u5728\u57f7\u884c JOIN \u67e5\u8a62\u6642\uff0c\u907f\u514d\u4f7f\u7528 SELECT *<\/code>\uff0c\u56e0\u70ba\u9019\u6703\u6aa2\u7d22\u6240\u6709\u6b04\u4f4d\uff0c\u589e\u52a0\u4e0d\u5fc5\u8981\u7684\u6578\u64da\u50b3\u8f38\u548c\u8655\u7406\u6642\u9593\u3002\u76f8\u53cd\uff0c\u61c9\u8a72\u53ea\u9078\u64c7\u9700\u8981\u7684\u6b04\u4f4d\u3002\u4f8b\u5982\uff1a<\/p>\n
SELECT u.name, o.amount\nFROM users u\nJOIN orders o ON u.user_id = o.user_id;\n<\/code><\/pre>\n
3. \u4f7f\u7528 INNER JOIN \u800c\u975e OUTER JOIN<\/h2>\n
\u5728\u53ef\u80fd\u7684\u60c5\u6cc1\u4e0b\uff0c\u4f7f\u7528 INNER JOIN<\/code> \u800c\u975e OUTER JOIN<\/code>\u3002INNER JOIN<\/code> \u53ea\u8fd4\u56de\u5169\u500b\u8868\u4e2d\u5339\u914d\u7684\u884c\uff0c\u9019\u901a\u5e38\u6703\u6bd4 OUTER JOIN<\/code> \u66f4\u5feb\uff0c\u56e0\u70ba\u5b83\u4e0d\u9700\u8981\u8655\u7406\u4e0d\u5339\u914d\u7684\u884c\u3002<\/p>\n
4. \u9650\u5236\u7d50\u679c\u96c6<\/h2>\n
\u5728\u67e5\u8a62\u4e2d\u4f7f\u7528 WHERE<\/code> \u5b50\u53e5\u4f86\u9650\u5236\u7d50\u679c\u96c6\u7684\u5927\u5c0f\uff0c\u53ef\u4ee5\u6e1b\u5c11\u9700\u8981\u8655\u7406\u7684\u6578\u64da\u91cf\uff0c\u5f9e\u800c\u63d0\u9ad8\u6027\u80fd\u3002\u4f8b\u5982\uff1a<\/p>\n
SELECT u.name, o.amount\nFROM users u\nJOIN orders o ON u.user_id = o.user_id\nWHERE o.amount > 100;\n<\/code><\/pre>\n
5. \u8003\u616e\u4f7f\u7528\u5b50\u67e5\u8a62<\/h2>\n
\u5728\u67d0\u4e9b\u60c5\u6cc1\u4e0b\uff0c\u4f7f\u7528\u5b50\u67e5\u8a62\u53ef\u80fd\u6703\u6bd4 JOIN \u66f4\u6709\u6548\u3002\u9019\u53d6\u6c7a\u65bc\u5177\u9ad4\u7684\u67e5\u8a62\u548c\u6578\u64da\u7d50\u69cb\u3002\u5b50\u67e5\u8a62\u53ef\u4ee5\u5e6b\u52a9\u6e1b\u5c11\u9700\u8981\u8655\u7406\u7684\u6578\u64da\u91cf\uff0c\u5f9e\u800c\u63d0\u9ad8\u6027\u80fd\u3002\u4f8b\u5982\uff1a<\/p>\n
SELECT name\nFROM users\nWHERE user_id IN (SELECT user_id FROM orders WHERE amount > 100);\n<\/code><\/pre>\n
6. \u5206\u6790\u67e5\u8a62\u8a08\u5283<\/h2>\n
\u4f7f\u7528\u8cc7\u6599\u5eab\u63d0\u4f9b\u7684\u67e5\u8a62\u5206\u6790\u5de5\u5177\u4f86\u6aa2\u67e5\u67e5\u8a62\u8a08\u5283\uff0c\u53ef\u4ee5\u5e6b\u52a9\u8b58\u5225\u6027\u80fd\u74f6\u9838\u3002\u5927\u591a\u6578\u8cc7\u6599\u5eab\u7cfb\u7d71\u90fd\u63d0\u4f9b\u4e86 EXPLAIN<\/code> \u547d\u4ee4\uff0c\u53ef\u4ee5\u986f\u793a\u67e5\u8a62\u7684\u57f7\u884c\u8a08\u5283\uff0c\u5e6b\u52a9\u958b\u767c\u8005\u4e86\u89e3\u67e5\u8a62\u7684\u904b\u884c\u65b9\u5f0f\uff0c\u4e26\u9032\u884c\u76f8\u61c9\u7684\u512a\u5316\u3002<\/p>\n
EXPLAIN SELECT u.name, o.amount\nFROM users u\nJOIN orders o ON u.user_id = o.user_id;\n<\/code><\/pre>\n
7. \u5b9a\u671f\u7dad\u8b77\u8cc7\u6599\u5eab<\/h2>\n
\u5b9a\u671f\u9032\u884c\u8cc7\u6599\u5eab\u7dad\u8b77\uff0c\u5982\u91cd\u5efa\u7d22\u5f15\u548c\u66f4\u65b0\u7d71\u8a08\u4fe1\u606f\uff0c\u53ef\u4ee5\u5e6b\u52a9\u4fdd\u6301\u8cc7\u6599\u5eab\u7684\u6027\u80fd\u3002\u96a8\u8457\u6578\u64da\u7684\u589e\u9577\uff0c\u7d22\u5f15\u53ef\u80fd\u6703\u8b8a\u5f97\u4e0d\u5920\u6709\u6548\uff0c\u56e0\u6b64\u5b9a\u671f\u7dad\u8b77\u662f\u5fc5\u8981\u7684\u3002<\/p>\n
\u7e3d\u7d50<\/h2>\n
\u512a\u5316 JOIN \u67e5\u8a62\u7684\u6027\u80fd\u662f\u4e00\u500b\u591a\u65b9\u9762\u7684\u904e\u7a0b\uff0c\u6d89\u53ca\u7d22\u5f15\u7684\u4f7f\u7528\u3001\u67e5\u8a62\u7d50\u69cb\u7684\u8a2d\u8a08\u4ee5\u53ca\u8cc7\u6599\u5eab\u7684\u7dad\u8b77\u3002\u901a\u904e\u4e0a\u8ff0\u65b9\u6cd5\uff0c\u958b\u767c\u8005\u53ef\u4ee5\u6709\u6548\u63d0\u9ad8\u67e5\u8a62\u7684\u57f7\u884c\u901f\u5ea6\uff0c\u5f9e\u800c\u63d0\u5347\u6574\u9ad4\u7cfb\u7d71\u7684\u6027\u80fd\u3002\u5982\u679c\u60a8\u9700\u8981\u66f4\u9ad8\u6548\u7684 VPS<\/a> \u89e3\u6c7a\u65b9\u6848\uff0c\u8acb\u8003\u616e\u6211\u5011\u7684\u670d\u52d9\uff0c\u8b93\u60a8\u7684\u8cc7\u6599\u5eab\u904b\u884c\u66f4\u52a0\u6d41\u66a2\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
\u63a2\u7d22\u63d0\u9ad8 SQL JOIN \u6548\u80fd\u7684\u6280\u5de7\uff0c\u5305\u62ec\u7d22\u5f15\u512a\u5316\u3001\u67e5\u8a62\u91cd\u69cb\u53ca\u8cc7\u6599\u5eab\u8a2d\u8a08\u6700\u4f73\u5be6\u8e10\uff0c\u8b93\u67e5\u8a62\u901f\u5ea6\u66f4\u5feb\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-174969","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/174969","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=174969"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/174969\/revisions"}],"predecessor-version":[{"id":174970,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/174969\/revisions\/174970"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=174969"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=174969"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=174969"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}