{"id":168163,"date":"2024-11-06T10:02:28","date_gmt":"2024-11-06T02:02:28","guid":{"rendered":"https:\/\/server.hk\/cnblog\/168163\/"},"modified":"2024-11-06T10:02:29","modified_gmt":"2024-11-06T02:02:29","slug":"%e5%85%ad%e5%80%8bsql%e6%9f%a5%e8%a9%a2%e6%8a%80%e5%b7%a7%ef%bc%8c%e4%bd%a0%e7%9f%a5%e9%81%93%e5%b9%be%e5%80%8b%ef%bc%9f","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/168163\/","title":{"rendered":"\u516d\u500bSQL\u67e5\u8a62\u6280\u5de7\uff0c\u4f60\u77e5\u9053\u5e7e\u500b\uff1f"},"content":{"rendered":"

\u516d\u500bSQL\u67e5\u8a62\u6280\u5de7\uff0c\u4f60\u77e5\u9053\u5e7e\u500b\uff1f<\/h1>\n

SQL\uff08\u7d50\u69cb\u5316\u67e5\u8a62\u8a9e\u8a00\uff09\u662f\u7528\u65bc\u7ba1\u7406\u548c\u64cd\u4f5c\u95dc\u4fc2\u578b\u6578\u64da\u5eab\u7684\u6a19\u6e96\u8a9e\u8a00\u3002\u7121\u8ad6\u662f\u6578\u64da\u5206\u6790\u3001\u61c9\u7528\u958b\u767c\u9084\u662f\u6578\u64da\u5eab\u7ba1\u7406\uff0c\u638c\u63e1\u4e00\u4e9b\u9ad8\u6548\u7684SQL\u67e5\u8a62\u6280\u5de7\u90fd\u80fd\u986f\u8457\u63d0\u9ad8\u5de5\u4f5c\u6548\u7387\u3002\u672c\u6587\u5c07\u4ecb\u7d39\u516d\u500b\u5be6\u7528\u7684SQL\u67e5\u8a62\u6280\u5de7\uff0c\u5e6b\u52a9\u4f60\u66f4\u597d\u5730\u5229\u7528SQL\u9032\u884c\u6578\u64da\u64cd\u4f5c\u3002<\/p>\n

1. \u4f7f\u7528\u7d22\u5f15\u63d0\u9ad8\u67e5\u8a62\u6548\u7387<\/h2>\n

\u7d22\u5f15\u662f\u6578\u64da\u5eab\u4e2d\u4e00\u7a2e\u7279\u6b8a\u7684\u6578\u64da\u7d50\u69cb\uff0c\u53ef\u4ee5\u52a0\u901f\u67e5\u8a62\u64cd\u4f5c\u3002\u7576\u4f60\u5728\u4e00\u500b\u5927\u578b\u8868\u4e2d\u9032\u884c\u67e5\u8a62\u6642\uff0c\u4f7f\u7528\u7d22\u5f15\u53ef\u4ee5\u986f\u8457\u6e1b\u5c11\u67e5\u8a62\u6642\u9593\u3002\u4f60\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b\u8a9e\u53e5\u5275\u5efa\u7d22\u5f15\uff1a<\/p>\n

CREATE INDEX idx_column_name ON table_name (column_name);<\/code><\/pre>\n
\u4f8b\u5982\uff0c\u5982\u679c\u4f60\u6709\u4e00\u500b\u540d\u70ba\u201cusers\u201d\u7684\u8868\uff0c\u4e26\u4e14\u7d93\u5e38\u6839\u64da\u201cemail\u201d\u5217\u9032\u884c\u67e5\u8a62\uff0c\u53ef\u4ee5\u9019\u6a23\u5275\u5efa\u7d22\u5f15\uff1a<\/p>\n
CREATE INDEX idx_email ON users (email);<\/code><\/pre>\n
2. \u4f7f\u7528JOIN\u8a9e\u53e5\u9032\u884c\u591a\u8868\u67e5\u8a62<\/h2>\n
\u5728\u6578\u64da\u5eab\u4e2d\uff0c\u6578\u64da\u901a\u5e38\u5206\u6563\u5728\u591a\u500b\u8868\u4e2d\u3002\u4f7f\u7528JOIN\u8a9e\u53e5\u53ef\u4ee5\u5c07\u9019\u4e9b\u8868\u4e2d\u7684\u6578\u64da\u806f\u5408\u8d77\u4f86\u3002\u6700\u5e38\u7528\u7684JOIN\u985e\u578b\u5305\u62ecINNER JOIN\u3001LEFT JOIN\u548cRIGHT JOIN\u3002\u4ee5\u4e0b\u662f\u4e00\u500bINNER JOIN\u7684\u793a\u4f8b\uff1a<\/p>\n
SELECT users.name, orders.amount \nFROM users \nINNER JOIN orders ON users.id = orders.user_id;<\/code><\/pre>\n
\u9019\u689d\u67e5\u8a62\u5c07\u8fd4\u56de\u6240\u6709\u7528\u6236\u53ca\u5176\u8a02\u55ae\u91d1\u984d\u3002<\/p>\n
3. \u4f7f\u7528\u5b50\u67e5\u8a62\u9032\u884c\u8907\u96dc\u67e5\u8a62<\/h2>\n
\u5b50\u67e5\u8a62\u662f\u5d4c\u5957\u5728\u5176\u4ed6\u67e5\u8a62\u4e2d\u7684\u67e5\u8a62\uff0c\u53ef\u4ee5\u7528\u4f86\u89e3\u6c7a\u66f4\u8907\u96dc\u7684\u554f\u984c\u3002\u4f8b\u5982\uff0c\u5047\u8a2d\u4f60\u60f3\u67e5\u8a62\u6240\u6709\u8a02\u55ae\u91d1\u984d\u5927\u65bc\u5e73\u5747\u91d1\u984d\u7684\u7528\u6236\uff0c\u53ef\u4ee5\u9019\u6a23\u5beb\uff1a<\/p>\n
SELECT * \nFROM users \nWHERE id IN (SELECT user_id FROM orders WHERE amount > (SELECT AVG(amount) FROM orders));<\/code><\/pre>\n
4. \u4f7f\u7528GROUP BY\u548cHAVING\u9032\u884c\u5206\u7d44\u67e5\u8a62<\/h2>\n
\u7576\u4f60\u9700\u8981\u5c0d\u67e5\u8a62\u7d50\u679c\u9032\u884c\u5206\u7d44\u4e26\u8a08\u7b97\u805a\u5408\u51fd\u6578\u6642\uff0c\u53ef\u4ee5\u4f7f\u7528GROUP BY\u8a9e\u53e5\u3002HAVING\u5b50\u53e5\u5247\u7528\u65bc\u904e\u6ffe\u5206\u7d44\u7d50\u679c\u3002\u4f8b\u5982\uff0c\u67e5\u8a62\u6bcf\u500b\u7528\u6236\u7684\u8a02\u55ae\u6578\u91cf\uff0c\u53ef\u4ee5\u9019\u6a23\u5beb\uff1a<\/p>\n
SELECT user_id, COUNT(*) as order_count \nFROM orders \nGROUP BY user_id \nHAVING COUNT(*) > 5;<\/code><\/pre>\n
\u9019\u689d\u67e5\u8a62\u5c07\u8fd4\u56de\u8a02\u55ae\u6578\u91cf\u5927\u65bc5\u7684\u7528\u6236\u3002<\/p>\n
5. \u4f7f\u7528CASE\u8a9e\u53e5\u9032\u884c\u689d\u4ef6\u67e5\u8a62<\/h2>\n
CASE\u8a9e\u53e5\u53ef\u4ee5\u5728\u67e5\u8a62\u4e2d\u5be6\u73fe\u689d\u4ef6\u908f\u8f2f\uff0c\u985e\u4f3c\u65bc\u5176\u4ed6\u7de8\u7a0b\u8a9e\u8a00\u4e2d\u7684if-else\u7d50\u69cb\u3002\u4ee5\u4e0b\u662f\u4e00\u500b\u793a\u4f8b\uff0c\u6839\u64da\u8a02\u55ae\u91d1\u984d\u8fd4\u56de\u4e0d\u540c\u7684\u72c0\u614b\uff1a<\/p>\n
SELECT amount, \nCASE \n    WHEN amount > 100 THEN '\u9ad8\u50f9'\n    WHEN amount BETWEEN 50 AND 100 THEN '\u4e2d\u50f9'\n    ELSE '\u4f4e\u50f9'\nEND as price_category \nFROM orders;<\/code><\/pre>\n
6. \u4f7f\u7528LIMIT\u548cOFFSET\u9032\u884c\u5206\u9801\u67e5\u8a62<\/h2>\n
\u5728\u8655\u7406\u5927\u91cf\u6578\u64da\u6642\uff0c\u5206\u9801\u67e5\u8a62\u53ef\u4ee5\u63d0\u9ad8\u7528\u6236\u9ad4\u9a57\u3002\u4f7f\u7528LIMIT\u548cOFFSET\u53ef\u4ee5\u63a7\u5236\u67e5\u8a62\u8fd4\u56de\u7684\u8a18\u9304\u6578\u91cf\u3002\u4f8b\u5982\uff0c\u67e5\u8a62\u7b2c2\u9801\u768410\u689d\u8a18\u9304\uff1a<\/p>\n
SELECT * \nFROM orders \nORDER BY created_at DESC \nLIMIT 10 OFFSET 10;<\/code><\/pre>\n
\u9019\u689d\u67e5\u8a62\u5c07\u8fd4\u56de\u7b2c11\u5230\u7b2c20\u689d\u8a02\u55ae\u8a18\u9304\u3002<\/p>\n
\u7e3d\u7d50<\/h2>\n
\u638c\u63e1\u9019\u4e9bSQL\u67e5\u8a62\u6280\u5de7\u53ef\u4ee5\u5e6b\u52a9\u4f60\u66f4\u9ad8\u6548\u5730\u9032\u884c\u6578\u64da\u64cd\u4f5c\uff0c\u7121\u8ad6\u662f\u5728\u6578\u64da\u5206\u6790\u9084\u662f\u61c9\u7528\u958b\u767c\u4e2d\u90fd\u80fd\u6d3e\u4e0a\u7528\u5834\u3002\u96a8\u8457\u6578\u64da\u91cf\u7684\u589e\u9577\uff0c\u5b78\u7fd2\u5982\u4f55\u512a\u5316\u67e5\u8a62\u548c\u63d0\u9ad8\u6027\u80fd\u8b8a\u5f97\u8d8a\u4f86\u8d8a\u91cd\u8981\u3002\u5982\u679c\u4f60\u9700\u8981\u7a69\u5b9a\u7684\u6578\u64da\u5eab\u74b0\u5883\u4f86\u904b\u884c\u4f60\u7684\u61c9\u7528\uff0c\u8003\u616e\u4f7f\u7528\u9999\u6e2fVPS<\/a>\u6216\u9999\u6e2f\u4f3a\u670d\u5668<\/a>\uff0c\u4ee5\u78ba\u4fdd\u4f60\u7684\u6578\u64da\u5b89\u5168\u548c\u9ad8\u6548\u5b58\u53d6\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
\u63a2\u7d22\u516d\u500b\u5be6\u7528\u7684SQL\u67e5\u8a62\u6280\u5de7\uff0c\u63d0\u5347\u4f60\u7684\u6578\u64da\u8655\u7406\u80fd\u529b\uff0c\u8b93\u67e5\u8a62\u66f4\u9ad8\u6548\u3001\u66f4\u7cbe\u6e96\uff01<\/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-168163","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/168163","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=168163"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/168163\/revisions"}],"predecessor-version":[{"id":168164,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/168163\/revisions\/168164"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=168163"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=168163"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=168163"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}