请教三表inner join，取其中一个表的前2个记录的问题

[unm]

SELECT a.content, a.postdate, c.username
FROM (
表1 a
INNER JOIN 表2 b ON a.uid = b.uid
)
INNER JOIN 表3 c ON a.uid = c.uid
ORDER BY username, postdate DESC
LIMIT 50

表1表2表三通过用户的uid关联

如果想取得每一个用户的前2条表1记录，怎么取得啊

[rucypli]

select *
from tb A
where (select count(*) from tb where A.username=b.username and A.id>b.id)>2

[ACMAIN_CHM]

参考下贴中的多种方法

http://topic.csdn.net/u/20091231/16/2f268740-391e-40f2-a15e-f243b2c925ab.html
[征集]分组取最大N条记录方法征集，及散分....

[rucypli]

select *
from tb A
where (select count(*) from tb b where A.username=b.username and A.id>b.id)<2

[ACMAIN_CHM]

SELECT a.content, a.postdate, c.username
FROM 表1 a INNER JOIN 表2 b ON a.uid = b.uid
	INNER JOIN 表3 c ON a.uid = c.uid
where 2>(select count(*) from 表1 where uid=a.uid and postdate>a.postdate)
ORDER BY username, postdate DESC  
LIMIT 50