{"id":143943,"date":"2024-11-01T02:33:19","date_gmt":"2024-10-31T18:33:19","guid":{"rendered":"https:\/\/server.hk\/cnblog\/143943\/"},"modified":"2024-11-01T02:33:20","modified_gmt":"2024-10-31T18:33:20","slug":"sql-%e6%95%b8%e6%93%9a%e5%ba%ab%e6%9f%a5%e8%a9%a2%e7%a8%8b%e5%ba%8f%e5%88%9d%e5%ad%b8%e8%80%85%e5%bf%85%e5%82%99%e6%8c%87%e5%8d%97-sql-%e6%95%b8%e6%93%9a%e5%ba%ab%e6%9f%a5%e8%a9%a2%e7%a8%8b%e5%ba%8f","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/143943\/","title":{"rendered":"SQL \u6578\u64da\u5eab\u67e5\u8a62\u7a0b\u5e8f\u521d\u5b78\u8005\u5fc5\u5099\u6307\u5357 (sql \u6578\u64da\u5eab\u67e5\u8a62\u7a0b\u5e8f)"},"content":{"rendered":"

SQL \u6578\u64da\u5eab\u67e5\u8a62\u7a0b\u5e8f\u521d\u5b78\u8005\u5fc5\u5099\u6307\u5357<\/h1>\n

\u5728\u7576\u4eca\u6578\u64da\u9a45\u52d5\u7684\u4e16\u754c\u4e2d\uff0cSQL\uff08\u7d50\u69cb\u5316\u67e5\u8a62\u8a9e\u8a00\uff09\u662f\u8207\u6578\u64da\u5eab\u9032\u884c\u4ea4\u4e92\u7684\u4e3b\u8981\u5de5\u5177\u4e4b\u4e00\u3002\u7121\u8ad6\u662f\u958b\u767c\u61c9\u7528\u7a0b\u5e8f\u3001\u6578\u64da\u5206\u6790\u9084\u662f\u7db2\u7ad9\u7ba1\u7406\uff0c\u638c\u63e1 SQL \u90fd\u662f\u5fc5\u4e0d\u53ef\u5c11\u7684\u6280\u80fd\u3002\u672c\u6587\u5c07\u70ba\u521d\u5b78\u8005\u63d0\u4f9b\u4e00\u500b\u5168\u9762\u7684 SQL \u6578\u64da\u5eab\u67e5\u8a62\u7a0b\u5e8f\u6307\u5357\uff0c\u5e6b\u52a9\u60a8\u5feb\u901f\u5165\u9580\u3002<\/p>\n

\u4ec0\u9ebc\u662f SQL\uff1f<\/h2>\n

SQL \u662f\u4e00\u7a2e\u5c08\u9580\u7528\u65bc\u7ba1\u7406\u548c\u64cd\u4f5c\u95dc\u4fc2\u578b\u6578\u64da\u5eab\u7684\u7de8\u7a0b\u8a9e\u8a00\u3002\u5b83\u5141\u8a31\u7528\u6236\u5275\u5efa\u3001\u8b80\u53d6\u3001\u66f4\u65b0\u548c\u522a\u9664\u6578\u64da\uff08\u901a\u5e38\u7c21\u7a31\u70ba CRUD \u64cd\u4f5c\uff09\u3002SQL \u7684\u8a9e\u6cd5\u7c21\u55ae\u660e\u77ad\uff0c\u4f7f\u5f97\u5373\u4f7f\u662f\u521d\u5b78\u8005\u4e5f\u80fd\u5920\u5feb\u901f\u4e0a\u624b\u3002<\/p>\n

\u57fa\u672c SQL \u67e5\u8a62\u8a9e\u6cd5<\/h2>\n

\u5728 SQL \u4e2d\uff0c\u6700\u57fa\u672c\u7684\u67e5\u8a62\u8a9e\u53e5\u662f SELECT<\/code> \u8a9e\u53e5\u3002\u9019\u500b\u8a9e\u53e5\u7528\u65bc\u5f9e\u6578\u64da\u5eab\u4e2d\u6aa2\u7d22\u6578\u64da\u3002\u4ee5\u4e0b\u662f\u57fa\u672c\u7684 SELECT<\/code> \u8a9e\u53e5\u7684\u7d50\u69cb\uff1a<\/p>\n

SELECT column1, column2, ...\nFROM table_name\nWHERE condition;<\/code><\/pre>\n
\u793a\u4f8b<\/h3>\n
\u5047\u8a2d\u6211\u5011\u6709\u4e00\u500b\u540d\u70ba employees<\/code> \u7684\u8868\uff0c\u5305\u542b\u4ee5\u4e0b\u5217\uff1aid<\/code>\u3001name<\/code> \u548c salary<\/code>\u3002\u5982\u679c\u6211\u5011\u60f3\u8981\u67e5\u8a62\u6240\u6709\u54e1\u5de5\u7684\u59d3\u540d\u548c\u85aa\u6c34\uff0c\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b SQL \u8a9e\u53e5\uff1a<\/p>\n
SELECT name, salary\nFROM employees;<\/code><\/pre>\n
\u904e\u6ffe\u6578\u64da<\/h2>\n
\u5728\u67e5\u8a62\u4e2d\uff0c\u60a8\u53ef\u4ee5\u4f7f\u7528 WHERE<\/code> \u5b50\u53e5\u4f86\u904e\u6ffe\u6578\u64da\u3002\u4f8b\u5982\uff0c\u5982\u679c\u60a8\u53ea\u60f3\u67e5\u8a62\u85aa\u6c34\u9ad8\u65bc 50000 \u7684\u54e1\u5de5\uff0c\u53ef\u4ee5\u9019\u6a23\u5beb\uff1a<\/p>\n
SELECT name, salary\nFROM employees\nWHERE salary > 50000;<\/code><\/pre>\n
\u6392\u5e8f\u7d50\u679c<\/h2>\n
\u4f7f\u7528 ORDER BY<\/code> \u5b50\u53e5\u53ef\u4ee5\u5c0d\u67e5\u8a62\u7d50\u679c\u9032\u884c\u6392\u5e8f\u3002\u9ed8\u8a8d\u60c5\u6cc1\u4e0b\uff0c\u6392\u5e8f\u662f\u5347\u5e8f\u7684\uff0c\u4f46\u60a8\u53ef\u4ee5\u4f7f\u7528 DESC<\/code> \u4f86\u9032\u884c\u964d\u5e8f\u6392\u5e8f\u3002<\/p>\n
SELECT name, salary\nFROM employees\nWHERE salary > 50000\nORDER BY salary DESC;<\/code><\/pre>\n
\u805a\u5408\u51fd\u6578<\/h2>\n
SQL \u63d0\u4f9b\u4e86\u591a\u7a2e\u805a\u5408\u51fd\u6578\uff0c\u4f8b\u5982 COUNT<\/code>\u3001SUM<\/code>\u3001AVG<\/code>\u3001MIN<\/code> \u548c MAX<\/code>\uff0c\u7528\u65bc\u8a08\u7b97\u6578\u64da\u7684\u7d71\u8a08\u4fe1\u606f\u3002<\/p>\n
\u793a\u4f8b<\/h3>\n
\u5982\u679c\u60a8\u60f3\u8a08\u7b97\u6240\u6709\u54e1\u5de5\u7684\u5e73\u5747\u85aa\u6c34\uff0c\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b\u8a9e\u53e5\uff1a<\/p>\n
SELECT AVG(salary) AS average_salary\nFROM employees;<\/code><\/pre>\n
\u5206\u7d44\u6578\u64da<\/h2>\n
\u4f7f\u7528 GROUP BY<\/code> \u5b50\u53e5\u53ef\u4ee5\u5c07\u7d50\u679c\u96c6\u6309\u67d0\u4e00\u5217\u9032\u884c\u5206\u7d44\uff0c\u4e26\u8207\u805a\u5408\u51fd\u6578\u4e00\u8d77\u4f7f\u7528\u3002\u4f8b\u5982\uff0c\u5982\u679c\u60a8\u60f3\u6309\u90e8\u9580\u8a08\u7b97\u6bcf\u500b\u90e8\u9580\u7684\u54e1\u5de5\u6578\u91cf\uff0c\u53ef\u4ee5\u9019\u6a23\u5beb\uff1a<\/p>\n
SELECT department, COUNT(*) AS employee_count\nFROM employees\nGROUP BY department;<\/code><\/pre>\n
\u7d50\u5408\u591a\u500b\u8868<\/h2>\n
\u5728\u5be6\u969b\u61c9\u7528\u4e2d\uff0c\u6578\u64da\u901a\u5e38\u5206\u4f48\u5728\u591a\u500b\u8868\u4e2d\u3002\u4f7f\u7528 JOIN<\/code> \u8a9e\u53e5\u53ef\u4ee5\u5c07\u9019\u4e9b\u8868\u7d50\u5408\u5728\u4e00\u8d77\u3002\u4f8b\u5982\uff0c\u5047\u8a2d\u6709\u4e00\u500b\u540d\u70ba departments<\/code> \u7684\u8868\uff0c\u60a8\u53ef\u4ee5\u901a\u904e\u4ee5\u4e0b\u65b9\u5f0f\u67e5\u8a62\u6bcf\u500b\u54e1\u5de5\u53ca\u5176\u6240\u5c6c\u90e8\u9580\uff1a<\/p>\n
SELECT employees.name, departments.department_name\nFROM employees\nJOIN departments ON employees.department_id = departments.id;<\/code><\/pre>\n
\u7e3d\u7d50<\/h2>\n
\u638c\u63e1 SQL \u67e5\u8a62\u8a9e\u8a00\u662f\u6578\u64da\u5eab\u7ba1\u7406\u548c\u6578\u64da\u5206\u6790\u7684\u57fa\u790e\u3002\u901a\u904e\u5b78\u7fd2\u57fa\u672c\u7684\u67e5\u8a62\u8a9e\u6cd5\u3001\u904e\u6ffe\u3001\u6392\u5e8f\u3001\u805a\u5408\u548c\u8868\u7684\u7d50\u5408\uff0c\u60a8\u5c07\u80fd\u5920\u6709\u6548\u5730\u5f9e\u6578\u64da\u5eab\u4e2d\u63d0\u53d6\u6240\u9700\u7684\u4fe1\u606f\u3002\u96a8\u8457\u60a8\u6280\u80fd\u7684\u63d0\u5347\uff0c\u60a8\u53ef\u4ee5\u9032\u4e00\u6b65\u63a2\u7d22\u66f4\u8907\u96dc\u7684\u67e5\u8a62\u548c\u6578\u64da\u5eab\u8a2d\u8a08\u3002<\/p>\n
\u5982\u679c\u60a8\u6b63\u5728\u5c0b\u627e\u53ef\u9760\u7684 \u9999\u6e2f VPS<\/a> \u89e3\u6c7a\u65b9\u6848\u4f86\u904b\u884c\u60a8\u7684\u6578\u64da\u5eab\uff0cServer.HK \u63d0\u4f9b\u591a\u7a2e\u9078\u64c7\uff0c\u6eff\u8db3\u4e0d\u540c\u9700\u6c42\u3002\u7121\u8ad6\u662f\u5c0f\u578b\u9805\u76ee\u9084\u662f\u5927\u578b\u4f01\u696d\u61c9\u7528\uff0c\u6211\u5011\u7684 \u4e91\u670d\u52d9\u5668<\/a> \u90fd\u80fd\u70ba\u60a8\u63d0\u4f9b\u7a69\u5b9a\u7684\u652f\u6301\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
\u638c\u63e1SQL\u6578\u64da\u5eab\u67e5\u8a62\u7684\u57fa\u790e\u77e5\u8b58\uff0c\u9019\u672c\u521d\u5b78\u8005\u5fc5\u5099\u6307\u5357\u5c07\u5e6b\u52a9\u4f60\u8f15\u9b06\u5b78\u7fd2\u548c\u61c9\u7528SQL\u67e5\u8a62\u6280\u5de7\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-143943","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/143943","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=143943"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/143943\/revisions"}],"predecessor-version":[{"id":143944,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/143943\/revisions\/143944"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=143943"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=143943"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=143943"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}