关于分组！

Question

select teacher,class,subject,datediff(minute,starttime,endtime) as hoursum
from tmclassroomclass
group by teacher,class,subject,datediff(minute,starttime,endtime)

Answer 1

select teacher,class,subject,sum(datediff(minute,starttime,endtime)) as hoursum
from tmclassroomclass
group by teacher,class,subject

Answer 2

上述两种,不知道楼主是那种意思慨念就是这样的,用group by 的话,在select 中出现的,凡是未包含在聚合函数(sum/max/min等)中的,都必须放在group by中

Answer 3

谢谢!  不出错  但是用你显示出的teacher有重复 不符合要求

Answer 4

select teacher,sum(datediff(minute,starttime,endtime)) as hoursum
from tmclassroomclass
group by teacher
看来只能 这样写了   
非常感谢zjcxc(邹建) 

Answer 5

肯定有重复了
要想没有重复，就把CLASS和SUBJECT去掉就可以了
select teacher sum(datediff(minute,starttime,endtime)) as hoursum
from tmclassroomclass
group by teacher

Answer 6

--如果只是按teacher分组
select teacher,class=max(class),subject,sum(datediff(minute,starttime,endtime)) as hoursum
from tmclassroomclass
group by teacher