SQL查询问题

laoleng

我现在用这样的语句查询出一个记录集，
select a.* from tablename a where datetimecolumn=(select max(datetimecolumn) from tablename where username=a.username)

然后我要跟一个叫erid的表做join 条件是查询出的结果中，username=erid.username
我试了直接做jion后还是只出来前面查询的结果erid表里的东西一个都每出来，这样写不是吗？那该怎样写？

trampzz

Is this right?
select a.*,e.* from tablename a
join erid e on e.username=erid.username
where a.datetimecolumn=(select max(datetimecolumn) from tablename where username=a.username)

yaeric

select a.*,e.* from tablename a
right join erid e on e.username=erid.username
where a.datetimecolumn=(select max(datetimecolumn) from tablename where username=a.username)
?

karaoke520

select a.*,b.* from tablename a
right join erid b on a.username=b.username
where a.datetimecolumn=(select max(datetimecolumn) from tablename where username=a.username)