Try to do it every day. SQL (ii) Count sum case-then-group by

1.

Select SUM (case if a.[status]=0 then 1 ELSE 0 End) as A1,
SUM (case A.[status] When 1 then 1 ELSE 0 end) as A2,
SUM (case A.[status] When 2 then 1 ELSE 0 end) as A3,

A.userid,c.trainid
From Coursewarelogmiddle A join Lessondetail B
On A.lessonid=b.id
Join Lessonclass C on B.classid=c.classid
where a.userid=9143 and c.trainid=81
GROUP BY A.userid,c.trainid

Row-to-column, although the case is used and then it needs to be used in conjunction with group.

The first sum I wrote is count but Count is will count all.

So decided to sum up, it is correct.

This method can calculate the quantity.