MySQL分组排序取前N条记录以及生成自动数字序列

-- MySQL分组排序取前N条记录的最简洁的单条sql。 N >(

结果如下：

mysql > SELECT * FROM (SELECT cid,author,COUNT(*) AS number FROM test GROUP BY cid,author) a -> WHERE -> 3>( -> SELECT COUNT(*) -> FROM (SELECT cid,author,COUNT(*) AS number FROM test GROUP BY cid,author) b -> WHERE a.cid=b.cid AND a.number<b.number -> )ORDER BY cid,number DESC; +------+----------------+--------+ | cid | author | number | +------+----------------+--------+ | 1 | test3 | 4 | | 1 | test2 | 3 | | 1 | test1 | 2 | | 2 | test33 | 4 | | 2 | test22 | 3 | | 2 | test11 | 2 | | 200 | 200test_nagios | 1 | +------+----------------+--------+ 7 rows in set (0.00 sec)

N就是取分组之后的最前面几个判断，N=3就是取前3个

 -- 生成自动数字序列 SET @ROW=0;

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