假设有这样一个表:表名sheet2,见图。
现在要查询每个type里的前2名,答案如下。
SELECT t1.*
FROM sheet2 AS t1
WHERE
( SELECT count(*) FROM sheet2 AS t2 WHERE t2.type = t1.type AND t2.times > t1.times )< 2
ORDER BY t1.type;
但是count那里是怎么回事呢?不理解。如果(select count(*)from sheet as t2 ......)<2,那么count(*)<2了,不就是t2只取前1个记录了吗?难道这个题,不应该是(select...t2...)<4?这样t2能取到前3个记录,而因为t2.type>t1.type,所以t1取到前2个记录。不应该是这样吗?
求解!