{"id":199666,"date":"2025-05-06T10:43:11","date_gmt":"2025-05-06T02:43:11","guid":{"rendered":"https:\/\/server.hk\/cnblog\/199666\/"},"modified":"2025-05-06T10:43:11","modified_gmt":"2025-05-06T02:43:11","slug":"group-by%e4%bb%80%e4%b9%88%e6%84%8f%e6%80%9d","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/199666\/","title":{"rendered":"group by\u4ec0\u4e48\u610f\u601d"},"content":{"rendered":"

<\/b> <\/p>\n

group by\u4ec0\u4e48\u610f\u601d<\/h1>\n<\/p>\n

Title: “Group by\u662f\u4ec0\u4e48\u610f\u601d\uff1f\u9700\u8981\u5177\u4f53\u4ee3\u7801\u793a\u4f8b”<\/p>\n

\u6b63\u6587\uff1a
\u5728\u6570\u636e\u5e93\u4e2d\uff0c”group by”\u662f\u7528\u6765\u5bf9\u6570\u636e\u8fdb\u884c\u5206\u7ec4\u7684\u4e00\u79cd\u64cd\u4f5c\u3002\u901a\u8fc7\u4f7f\u7528”group by”\u5173\u952e\u5b57\uff0c\u6211\u4eec\u53ef\u4ee5\u6309\u7167\u7279\u5b9a\u7684\u5217\u6216\u8868\u8fbe\u5f0f\u5bf9\u6570\u636e\u8fdb\u884c\u5206\u7ec4\uff0c\u5e76\u5bf9\u6bcf\u4e2a\u7ec4\u8fdb\u884c\u805a\u5408\u8ba1\u7b97\u3002<\/p>\n

“group by”\u8bed\u53e5\u901a\u5e38\u4e0e”select”\u8bed\u53e5\u4e00\u8d77\u4f7f\u7528\uff0c\u4ee5\u4fbf\u5728\u9009\u62e9\u7279\u5b9a\u7684\u5217\u65f6\u5bf9\u6570\u636e\u8fdb\u884c\u5206\u7ec4\u3002\u5b83\u53ef\u4ee5\u8ba9\u6211\u4eec\u6309\u7167\u6307\u5b9a\u7684\u5217\u5bf9\u6570\u636e\u8fdb\u884c\u5206\u7ec4\uff0c\u5e76\u4e14\u5bf9\u6bcf\u4e2a\u7ec4\u8fdb\u884c\u805a\u5408\u64cd\u4f5c\uff0c\u5982\u6c42\u548c\u3001\u8ba1\u6570\u3001\u6c42\u5e73\u5747\u503c\u7b49\u3002\u8fd9\u6837\u53ef\u4ee5\u65b9\u4fbf\u5730\u5bf9\u6570\u636e\u8fdb\u884c\u7edf\u8ba1\u548c\u5206\u6790\uff0c\u5f97\u5230\u66f4\u6709\u610f\u4e49\u7684\u7ed3\u679c\u3002<\/p>\n

\u4e0b\u9762\u901a\u8fc7\u5177\u4f53\u7684\u4ee3\u7801\u793a\u4f8b\u6765\u8bf4\u660e”group by”\u7684\u4f7f\u7528\u3002<\/p>\n

\u5047\u8bbe\u6211\u4eec\u6709\u4e00\u4e2a\u540d\u4e3a”students”\u7684\u8868\uff0c\u5305\u542b\u4ee5\u4e0b\u51e0\u5217\uff1aid\u3001name\u3001age\u548cscore\u3002\u6211\u4eec\u60f3\u8981\u6309\u7167\u5e74\u9f84\u5206\u7ec4\uff0c\u8ba1\u7b97\u6bcf\u4e2a\u5e74\u9f84\u6bb5\u5185\u7684\u5b66\u751f\u4eba\u6570\u548c\u5e73\u5747\u5206\u6570\u3002<\/p>\n

\u9996\u5148\uff0c\u6211\u4eec\u53ef\u4ee5\u521b\u5efa\u4e00\u4e2a\u793a\u4f8b\u8868\u5e76\u63d2\u5165\u4e00\u4e9b\u6570\u636e\u3002<\/p>\n

CREATE TABLE students (\n    id INT PRIMARY KEY,\n    name VARCHAR(50),\n    age INT,\n    score FLOAT\n);\n\nINSERT INTO students VALUES (1, 'Tom', 15, 90.5);\nINSERT INTO students VALUES (2, 'Jerry', 16, 85.0);\nINSERT INTO students VALUES (3, 'Alice', 15, 92.0);\nINSERT INTO students VALUES (4, 'Bob', 14, 88.5);\nINSERT INTO students VALUES (5, 'Lucy', 16, 95.5);\nINSERT INTO students VALUES (6, 'John', 15, 91.0);<\/pre>\n
\u63a5\u4e0b\u6765\uff0c\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528”group by”\u8bed\u53e5\u6309\u7167\u5e74\u9f84\u5206\u7ec4\uff0c\u5e76\u8ba1\u7b97\u6bcf\u4e2a\u5e74\u9f84\u6bb5\u5185\u7684\u5b66\u751f\u4eba\u6570\u548c\u5e73\u5747\u5206\u6570\u3002<\/p>\n
SELECT age, COUNT(*) AS student_count, AVG(score) AS average_score\nFROM students\nGROUP BY age;<\/pre>\n
\u6267\u884c\u4ee5\u4e0a\u4ee3\u7801\u540e\uff0c\u6211\u4eec\u5c06\u5f97\u5230\u4ee5\u4e0b\u7ed3\u679c\uff1a<\/p>\n
age | student_count | average_score\n----|---------------|--------------\n14  |   1           |   88.5\n15  |   3           |   91.5\n16  |   2           |   90.25<\/pre>\n
\u4ee5\u4e0a\u7ed3\u679c\u663e\u793a\u4e86\u6bcf\u4e2a\u5e74\u9f84\u6bb5\u5185\u7684\u5b66\u751f\u4eba\u6570\u548c\u5e73\u5747\u5206\u6570\u3002<\/p>\n
\u901a\u8fc7\u4ee5\u4e0a\u793a\u4f8b\u53ef\u4ee5\u770b\u51fa\uff0c\u901a\u8fc7\u4f7f\u7528”group by”\u8bed\u53e5\uff0c\u6211\u4eec\u53ef\u4ee5\u5f88\u65b9\u4fbf\u5730\u5bf9\u6570\u636e\u8fdb\u884c\u5206\u7ec4\uff0c\u5e76\u5bf9\u6bcf\u4e2a\u7ec4\u8fdb\u884c\u8ba1\u7b97\u3002\u8fd9\u5bf9\u4e8e\u6570\u636e\u5206\u6790\u548c\u7edf\u8ba1\u662f\u975e\u5e38\u6709\u7528\u7684\u3002<\/p>\n
\u9700\u8981\u6ce8\u610f\u7684\u662f\uff0c\u5728”group by”\u8bed\u53e5\u4e2d\uff0c\u9664\u4e86\u53ef\u4ee5\u4f7f\u7528\u5217\u540d\u6765\u8fdb\u884c\u5206\u7ec4\u5916\uff0c\u8fd8\u53ef\u4ee5\u4f7f\u7528\u8868\u8fbe\u5f0f\u6765\u8fdb\u884c\u5206\u7ec4\u3002\u8fd9\u4e3a\u6211\u4eec\u63d0\u4f9b\u4e86\u66f4\u52a0\u7075\u6d3b\u7684\u64cd\u4f5c\u65b9\u5f0f\u3002<\/p>\n
\u603b\u7ed3\uff1a
\u901a\u8fc7\u672c\u6587\u7684\u4ecb\u7ecd\uff0c\u6211\u4eec\u4e86\u89e3\u4e86”group by”\u7684\u4f7f\u7528\u65b9\u6cd5\u548c\u610f\u4e49\u3002\u5b83\u53ef\u4ee5\u5e2e\u52a9\u6211\u4eec\u5bf9\u6570\u636e\u8fdb\u884c\u5206\u7ec4\uff0c\u5e76\u4e14\u5728\u6bcf\u4e2a\u7ec4\u5185\u8fdb\u884c\u805a\u5408\u64cd\u4f5c\u3002\u901a\u8fc7\u5177\u4f53\u7684\u4ee3\u7801\u793a\u4f8b\uff0c\u6211\u4eec\u5c55\u793a\u4e86\u5982\u4f55\u4f7f\u7528”group by”\u6765\u8ba1\u7b97\u6bcf\u4e2a\u5e74\u9f84\u6bb5\u5185\u7684\u5b66\u751f\u4eba\u6570\u548c\u5e73\u5747\u5206\u6570\u3002”group by”\u7684\u4f7f\u7528\u53ef\u4ee5\u8ba9\u6211\u4eec\u66f4\u52a0\u65b9\u4fbf\u5730\u8fdb\u884c\u6570\u636e\u7684\u7edf\u8ba1\u548c\u5206\u6790\uff0c\u5f97\u5230\u66f4\u52a0\u6709\u610f\u4e49\u7684\u7ed3\u679c\u3002<\/p>\n
\u597d\u4e86\uff0c\u672c\u6587\u5230\u6b64\u7ed3\u675f\uff0c\u5e26\u5927\u5bb6\u4e86\u89e3\u4e86\u300agroup by\u4ec0\u4e48\u610f\u601d\u300b\uff0c\u5e0c\u671b\u672c\u6587\u5bf9\u4f60\u6709\u6240\u5e2e\u52a9\uff01\u5173\u6ce8\u4e3b\u673a\u5b9d\u8d1d\u516c\u4f17\u53f7\uff0c\u7ed9\u5927\u5bb6\u5206\u4eab\u66f4\u591a\u6570\u636e\u5e93\u77e5\u8bc6\uff01<\/p>\n
\n
\n <\/dt>\n<\/dl>\n","protected":false},"excerpt":{"rendered":"
group by\u4ec0\u4e48\u610f\u601d Tit...<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[101],"tags":[],"class_list":["post-199666","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/199666","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"}],"author":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/comments?post=199666"}],"version-history":[{"count":0,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/199666\/revisions"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=199666"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=199666"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=199666"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}