MySQL分组排序求Top N
表结构
按照grp分组,按照num排序,每组取Top 3,输出结果如下:
源代码:
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SELECT * FROM score AS t3 WHERE ( SELECT COUNT (*) FROM score AS t1 LEFT JOIN score AS t2 ON t1.grp = t2.grp AND t1.num < t2.num WHERE t1.id = t3.id ) < 3 ORDER BY t3.grp ASC , num DESC |
在where中可以通过子查询创造一个新的变量来过滤。
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