请教sql语句

rtmx01

请教sql语句

select a.x1,a.x2,b.t1,b.t2

from (select x1,x2 from x) as a,(select (t1,t2 from t) as b

where a.x1=b.t1

该语句运行成功

但

select a.x1,a.x2,b.t1,b.t2

from (select x1,x2 from x) as a,(select (t1,t2 from t) as b

where a.x1=b.t1

group by b.t2

运行出错

请问怎么样修改

sgrshh29

不把为什么要group by b.t2的来龙去脉讲清楚，怎么改也是错的。

rtmx01

楼上高手,怎样才能说明白group by b.t2啊,我就是要按b.t2分组的啊