{"id":163691,"date":"2024-11-05T01:37:27","date_gmt":"2024-11-04T17:37:27","guid":{"rendered":"https:\/\/server.hk\/cnblog\/163691\/"},"modified":"2024-11-05T01:37:28","modified_gmt":"2024-11-04T17:37:28","slug":"%e8%a7%a3%e6%b1%basql-server%e4%b8%adgroup%e7%84%a1%e6%b3%95%e5%af%a6%e7%8f%be%e7%9a%84%e5%95%8f%e9%a1%8c","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/163691\/","title":{"rendered":"\u89e3\u6c7aSQL Server\u4e2dGroup\u7121\u6cd5\u5be6\u73fe\u7684\u554f\u984c"},"content":{"rendered":"

\u89e3\u6c7aSQL Server\u4e2dGroup\u7121\u6cd5\u5be6\u73fe\u7684\u554f\u984c<\/h1>\n

\u5728\u4f7f\u7528SQL Server\u9032\u884c\u6578\u64da\u67e5\u8a62\u6642\uff0cGROUP BY\u8a9e\u53e5\u662f\u975e\u5e38\u5e38\u898b\u7684\u64cd\u4f5c\u3002\u5b83\u80fd\u5920\u5e6b\u52a9\u7528\u6236\u5c0d\u6578\u64da\u9032\u884c\u5206\u7d44\uff0c\u4e26\u9032\u884c\u805a\u5408\u8a08\u7b97\u3002\u7136\u800c\uff0c\u5728\u67d0\u4e9b\u60c5\u6cc1\u4e0b\uff0c\u4f7f\u7528GROUP BY\u53ef\u80fd\u6703\u9047\u5230\u4e00\u4e9b\u554f\u984c\uff0c\u5c0e\u81f4\u7121\u6cd5\u5be6\u73fe\u9810\u671f\u7684\u7d50\u679c\u3002\u672c\u6587\u5c07\u63a2\u8a0e\u9019\u4e9b\u554f\u984c\u7684\u539f\u56e0\u53ca\u5176\u89e3\u6c7a\u65b9\u6848\u3002<\/p>\n

GROUP BY\u7684\u57fa\u672c\u6982\u5ff5<\/h2>\n

GROUP BY\u8a9e\u53e5\u7684\u4e3b\u8981\u529f\u80fd\u662f\u5c07\u67e5\u8a62\u7d50\u679c\u4e2d\u7684\u6578\u64da\u884c\u6839\u64da\u4e00\u500b\u6216\u591a\u500b\u5217\u9032\u884c\u5206\u7d44\u3002\u9019\u6a23\uff0c\u7528\u6236\u53ef\u4ee5\u5c0d\u6bcf\u500b\u5206\u7d44\u9032\u884c\u805a\u5408\u8a08\u7b97\uff0c\u4f8b\u5982\u8a08\u7b97\u7e3d\u548c\u3001\u5e73\u5747\u503c\u3001\u8a08\u6578\u7b49\u3002\u4ee5\u4e0b\u662f\u4e00\u500b\u57fa\u672c\u7684GROUP BY\u8a9e\u53e5\u793a\u4f8b\uff1a<\/p>\n

SELECT department, COUNT(*) AS employee_count\nFROM employees\nGROUP BY department;<\/code><\/pre>\n
\u9019\u6bb5\u4ee3\u78bc\u5c07\u6839\u64da\u90e8\u9580\u5c0d\u54e1\u5de5\u9032\u884c\u5206\u7d44\uff0c\u4e26\u8a08\u7b97\u6bcf\u500b\u90e8\u9580\u7684\u54e1\u5de5\u6578\u91cf\u3002<\/p>\n
\u5e38\u898b\u7684GROUP BY\u554f\u984c<\/h2>\n
1. \u7121\u6cd5\u5206\u7d44\u7684\u5217<\/h3>\n
\u5728\u4f7f\u7528GROUP BY\u6642\uff0c\u6240\u6709\u672a\u805a\u5408\u7684\u5217\u5fc5\u9808\u51fa\u73fe\u5728GROUP BY\u5b50\u53e5\u4e2d\u3002\u5982\u679c\u67e5\u8a62\u4e2d\u5305\u542b\u672a\u5206\u7d44\u7684\u5217\uff0cSQL Server\u5c07\u8fd4\u56de\u932f\u8aa4\u3002\u4f8b\u5982\uff1a<\/p>\n
SELECT department, employee_name, COUNT(*) AS employee_count\nFROM employees\nGROUP BY department;<\/code><\/pre>\n
\u5728\u9019\u500b\u4f8b\u5b50\u4e2d\uff0cemployee_name\u672a\u88ab\u5206\u7d44\uff0c\u9019\u5c07\u5c0e\u81f4\u932f\u8aa4\u3002\u89e3\u6c7a\u65b9\u6848\u662f\u5c07employee_name\u79fb\u9664\uff0c\u6216\u5c07\u5176\u6dfb\u52a0\u5230GROUP BY\u5b50\u53e5\u4e2d\u3002<\/p>\n
2. \u805a\u5408\u51fd\u6578\u7684\u4f7f\u7528<\/h3>\n
\u5728GROUP BY\u67e5\u8a62\u4e2d\uff0c\u805a\u5408\u51fd\u6578\u7684\u4f7f\u7528\u5fc5\u9808\u6b63\u78ba\u3002\u5982\u679c\u4f7f\u7528\u4e86\u4e0d\u6b63\u78ba\u7684\u805a\u5408\u51fd\u6578\uff0c\u53ef\u80fd\u6703\u5c0e\u81f4\u4e0d\u6b63\u78ba\u7684\u7d50\u679c\u3002\u4f8b\u5982\uff0c\u4f7f\u7528SUM\u51fd\u6578\u8a08\u7b97\u975e\u6578\u503c\u5217\u5c07\u5c0e\u81f4\u932f\u8aa4\u3002\u78ba\u4fdd\u805a\u5408\u51fd\u6578\u7684\u4f7f\u7528\u8207\u6578\u64da\u985e\u578b\u76f8\u7b26\u662f\u975e\u5e38\u91cd\u8981\u7684\u3002<\/p>\n
3. NULL\u503c\u7684\u8655\u7406<\/h3>\n
\u5728\u9032\u884c\u5206\u7d44\u6642\uff0cNULL\u503c\u7684\u5b58\u5728\u53ef\u80fd\u6703\u5f71\u97ff\u7d50\u679c\u3002SQL Server\u6703\u5c07\u6240\u6709NULL\u503c\u8996\u70ba\u4e00\u500b\u7d44\uff0c\u9019\u53ef\u80fd\u6703\u5c0e\u81f4\u610f\u5916\u7684\u7d50\u679c\u3002\u5982\u679c\u9700\u8981\u6392\u9664NULL\u503c\uff0c\u53ef\u4ee5\u5728\u67e5\u8a62\u4e2d\u4f7f\u7528WHERE\u5b50\u53e5\u9032\u884c\u904e\u6ffe\uff1a<\/p>\n
SELECT department, COUNT(*) AS employee_count\nFROM employees\nWHERE department IS NOT NULL\nGROUP BY department;<\/code><\/pre>\n
\u89e3\u6c7a\u65b9\u6848\u8207\u6700\u4f73\u5be6\u8e10<\/h2>\n
1. \u6aa2\u67e5GROUP BY\u5b50\u53e5<\/h3>\n
\u5728\u64b0\u5beb\u67e5\u8a62\u6642\uff0c\u9996\u5148\u6aa2\u67e5GROUP BY\u5b50\u53e5\uff0c\u78ba\u4fdd\u6240\u6709\u672a\u805a\u5408\u7684\u5217\u90fd\u5df2\u6b63\u78ba\u5217\u51fa\u3002\u9019\u6a23\u53ef\u4ee5\u907f\u514d\u56e0\u70ba\u5217\u672a\u5206\u7d44\u800c\u5c0e\u81f4\u7684\u932f\u8aa4\u3002<\/p>\n
2. \u4f7f\u7528HAVING\u5b50\u53e5<\/h3>\n
\u5728\u67d0\u4e9b\u60c5\u6cc1\u4e0b\uff0c\u60a8\u53ef\u80fd\u9700\u8981\u5c0d\u5206\u7d44\u5f8c\u7684\u7d50\u679c\u9032\u884c\u9032\u4e00\u6b65\u904e\u6ffe\u3002\u9019\u6642\u53ef\u4ee5\u4f7f\u7528HAVING\u5b50\u53e5\u3002\u4f8b\u5982\uff1a<\/p>\n
SELECT department, COUNT(*) AS employee_count\nFROM employees\nGROUP BY department\nHAVING COUNT(*) > 5;<\/code><\/pre>\n
\u9019\u6bb5\u4ee3\u78bc\u5c07\u50c5\u8fd4\u56de\u54e1\u5de5\u6578\u91cf\u5927\u65bc5\u7684\u90e8\u9580\u3002<\/p>\n
3. \u6e2c\u8a66\u8207\u9a57\u8b49<\/h3>\n
\u5728\u57f7\u884c\u8907\u96dc\u7684GROUP BY\u67e5\u8a62\u4e4b\u524d\uff0c\u5efa\u8b70\u5148\u9032\u884c\u5c0f\u7bc4\u570d\u7684\u6e2c\u8a66\uff0c\u4ee5\u78ba\u4fdd\u67e5\u8a62\u7684\u6b63\u78ba\u6027\u3002\u53ef\u4ee5\u4f7f\u7528LIMIT\u6216TOP\u8a9e\u53e5\u4f86\u9650\u5236\u8fd4\u56de\u7684\u884c\u6578\uff0c\u4fbf\u65bc\u6aa2\u67e5\u7d50\u679c\u3002<\/p>\n
\u7e3d\u7d50<\/h2>\n
\u5728SQL Server\u4e2d\uff0cGROUP BY\u662f\u4e00\u500b\u5f37\u5927\u7684\u5de5\u5177\uff0c\u4f46\u5728\u4f7f\u7528\u6642\u9700\u8981\u6ce8\u610f\u4e00\u4e9b\u5e38\u898b\u7684\u554f\u984c\u3002\u901a\u904e\u6b63\u78ba\u7684\u8a9e\u6cd5\u3001\u9069\u7576\u7684\u805a\u5408\u51fd\u6578\u4ee5\u53ca\u5c0dNULL\u503c\u7684\u8655\u7406\uff0c\u53ef\u4ee5\u6709\u6548\u5730\u89e3\u6c7a\u9019\u4e9b\u554f\u984c\u3002\u5c0d\u65bc\u9700\u8981\u9ad8\u6548\u6578\u64da\u8655\u7406\u7684\u7528\u6236\uff0c\u9078\u64c7\u5408\u9069\u7684\u9999\u6e2fVPS<\/a><\/code>\u6216\u96f2\u4f3a\u670d\u5668<\/a><\/code>\u89e3\u6c7a\u65b9\u6848\u5c07\u6709\u52a9\u65bc\u63d0\u5347\u6578\u64da\u5eab\u6027\u80fd\uff0c\u78ba\u4fdd\u67e5\u8a62\u7684\u5feb\u901f\u97ff\u61c9\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
\u89e3\u6c7aSQL Server\u4e2dGroup\u7121\u6cd5\u5be6\u73fe\u7684\u554f\u984c\uff0c\u63d0\u4f9b\u6709\u6548\u7684\u6280\u5de7\u8207\u65b9\u6cd5\uff0c\u5e6b\u52a9\u60a8\u512a\u5316\u67e5\u8a62\u8207\u6578\u64da\u5206\u6790\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-163691","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/163691","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=163691"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/163691\/revisions"}],"predecessor-version":[{"id":163692,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/163691\/revisions\/163692"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=163691"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=163691"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=163691"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}