{"id":200943,"date":"2025-05-06T13:12:31","date_gmt":"2025-05-06T05:12:31","guid":{"rendered":"https:\/\/server.hk\/cnblog\/200943\/"},"modified":"2025-05-06T13:12:31","modified_gmt":"2025-05-06T05:12:31","slug":"%e5%a6%82%e4%bd%95%e6%89%be%e5%87%ba%e9%97%ae%e7%ad%94%e7%b3%bb%e7%bb%9f%e4%b8%ad%e6%af%8f%e4%b8%aa%e9%97%ae%e9%a2%98%e8%a2%ab%e5%a4%8d%e5%88%b6%e6%ac%a1%e6%95%b0%e6%9c%80%e5%a4%9a%e7%9a%84%e7%ad%94","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/200943\/","title":{"rendered":"\u5982\u4f55\u627e\u51fa\u95ee\u7b54\u7cfb\u7edf\u4e2d\u6bcf\u4e2a\u95ee\u9898\u88ab\u590d\u5236\u6b21\u6570\u6700\u591a\u7684\u7b54\u6848\uff1f"},"content":{"rendered":"

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

\u5982\u4f55\u627e\u51fa\u95ee\u7b54\u7cfb\u7edf\u4e2d\u6bcf\u4e2a\u95ee\u9898\u88ab\u590d\u5236\u6b21\u6570\u6700\u591a\u7684\u7b54\u6848\uff1f<\/h1>\n<\/p>\n

<\/p>\n

mysql\u7ed3\u679c\u4e0e\u9884\u671f\u4e0d\u7b26\uff1a\u627e\u51fa\u7b54\u6848\u88ab\u590d\u5236\u6b21\u6570\u6700\u591a\u7684<\/strong><\/p>\n

\u5728\u4e00\u4e2a\u95ee\u7b54\u7cfb\u7edf\u4e2d\uff0c\u6211\u4eec\u9700\u8981\u627e\u51fa\u6bcf\u4e2a\u95ee\u9898\u4e0b\u88ab\u590d\u5236\u6b21\u6570\u6700\u591a\u7684\u7b54\u6848\u3002\u539f\u59cb\u67e5\u8be2\u5982\u4e0b\uff1a<\/p>\n

select question_id, answer_id, max(copy_count) as max_copy_count\nfrom answer_copy_count\ngroup by question_id;<\/pre>\n
\u7136\u800c\uff0c\u67e5\u8be2\u7ed3\u679c\u4ee4\u4eba\u56f0\u60d1\uff0c\u56e0\u4e3a\u67d0\u4e9b\u7b54\u6848\u7684 answer_id \u660e\u663e\u4e0d\u6b63\u786e\u3002<\/p>\n
\u4e3a\u4e86\u89e3\u51b3\u8fd9\u4e2a\u95ee\u9898\uff0c\u6211\u4eec\u9700\u8981\u8003\u8651\u4fee\u6539\u67e5\u8be2\u4ee5\u5728 group by \u5b50\u53e5\u4e2d\u5305\u542b\u989d\u5916\u7684\u5217\u3002\u4f46\u8fd9\u6837\u505a\u5374\u5e76\u4e0d\u80fd\u89e3\u51b3\u95ee\u9898\u3002<\/p>\n
\u8fd9\u91cc\u6211\u4eec\u4ecb\u7ecd\u4e00\u4e2a\u4e0d\u540c\u7684\u89e3\u51b3\u65b9\u6848\uff0c\u9002\u7528\u4e8e mysql 8.0 \u53ca\u66f4\u9ad8\u7248\u672c\uff1a\u4f7f\u7528\u7a97\u53e3\u51fd\u6570\u3002<\/p>\n
\u7a97\u53e3\u51fd\u6570<\/strong><\/p>\n
\u7a97\u53e3\u51fd\u6570\u53ef\u4ee5\u5728\u67e5\u8be2\u7ed3\u679c\u4e2d\u5bf9\u6307\u5b9a\u884c\u6216\u7ec4\u8fdb\u884c\u8ba1\u7b97\u3002\u5728\u672c\u4f8b\u4e2d\uff0c\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528 row_number() \u51fd\u6570\u6216 rank() \u51fd\u6570\u6765\u5bf9\u6bcf\u4e2a\u95ee\u9898\u4e0b\u590d\u5236\u6b21\u6570\u76f8\u540c\u7684\u6240\u6709\u7b54\u6848\u8fdb\u884c\u8ba1\u6570\uff0c\u7136\u540e\u53ea\u9009\u62e9\u6392\u540d\u7b2c\u4e00\u7684\u7b54\u6848\u3002<\/p>\n
\u4f7f\u7528 row_number() \u51fd\u6570<\/strong><\/p>\n
row_number() \u51fd\u6570\u6309\u6307\u5b9a\u987a\u5e8f\u751f\u6210\u884c\u7f16\u53f7\uff0c\u5728\u6b64\u60c5\u51b5\u4e0b\u6309\u590d\u5236\u6b21\u6570\u964d\u5e8f\u6392\u5e8f\u3002<\/p>\n
select *\nfrom (\n  select question_id, answer_id, copy_count,\n    row_number() over (partition by question_id order by copy_count desc) as idx\n  from answer_copy_count\n) t\nwhere idx = 1;<\/pre>\n
\u6b64\u67e5\u8be2\u5c06\u4ec5\u8fd4\u56de\u6bcf\u4e2a\u95ee\u9898\u4e0b\u590d\u5236\u6b21\u6570\u6700\u591a\u7684\u7b54\u6848\u3002<\/p>\n
\u4f7f\u7528 rank() \u51fd\u6570<\/strong><\/p>\n
rank() \u51fd\u6570\u7c7b\u4f3c\u4e8e row_number() \u51fd\u6570\uff0c\u4f46\u5b83\u4f1a\u4e3a\u590d\u5236\u6b21\u6570\u76f8\u540c\u7684\u7b54\u6848\u5206\u914d\u76f8\u540c\u7684\u6392\u540d\u3002<\/p>\n
SELECT *\nFROM (\n  SELECT question_id, answer_id, copy_count,\n    rank() OVER (PARTITION BY question_id ORDER BY copy_count DESC) AS idx\n  FROM answer_copy_count\n) t\nWHERE idx = 1;<\/pre>\n
\u6b64\u67e5\u8be2\u5c06\u8fd4\u56de\u6bcf\u4e2a\u95ee\u9898\u4e0b\u590d\u5236\u6b21\u6570\u76f8\u540c\u7684\u7b54\u6848\u3002<\/p>\n
\u7ec8\u4e8e\u4ecb\u7ecd\u5b8c\u5566\uff01\u5c0f\u4f19\u4f34\u4eec\uff0c\u8fd9\u7bc7\u5173\u4e8e\u300a\u5982\u4f55\u627e\u51fa\u95ee\u7b54\u7cfb\u7edf\u4e2d\u6bcf\u4e2a\u95ee\u9898\u88ab\u590d\u5236\u6b21\u6570\u6700\u591a\u7684\u7b54\u6848\uff1f\u300b\u7684\u4ecb\u7ecd\u5e94\u8be5\u8ba9\u4f60\u6536\u83b7\u591a\u591a\u4e86\u5427\uff01\u6b22\u8fce\u5927\u5bb6\u6536\u85cf\u6216\u5206\u4eab\u7ed9\u66f4\u591a\u9700\u8981\u5b66\u4e60\u7684\u670b\u53cb\u5427~\u4e3b\u673a\u5b9d\u8d1d\u516c\u4f17\u53f7\u4e5f\u4f1a\u53d1\u5e03\u6570\u636e\u5e93\u76f8\u5173\u77e5\u8bc6\uff0c\u5feb\u6765\u5173\u6ce8\u5427\uff01<\/p>\n
\n
\n <\/dt>\n<\/dl>\n","protected":false},"excerpt":{"rendered":"
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