선택 SUM은

Question

나는이 쿼리가 성공적으로 totstock

SELECT p.pid,p.product_name,SUM(s.qty) as totstock 
FROM tblproducts p 
LEFT JOIN tblstocks s ON s.pid=p.pid 
GROUP BY p.pid 

얻을하지만 난 내 두 번째 테이블을 결합하려고 할 때 잘못 총 totstock 및 totsales 내가이 쿼리를 가지고 있지만 내가 그것을 생각 얻는다 잘못된

SELECT p.pid,p.product_name,SUM(s.qty) as totstock,SUM(sl.qty) as totsale 
FROM tblproducts p 
LEFT JOIN tblstocks s ON s.pid=p.pid 
LEFT JOIN tbls sl ON sl.pid=p.pid 
GROUP BY p.pid 

제품입니다 -

pid | product_name 
1 | pencil 
2 | paper 

tblproducts

주식 - tblstocks

pid | qty 
1 | 1 
1 | 3 
1 | 5 

판매 - tbls

pid | qty 
    1 | 2 
    1 | 1 

내가 원하는 결과

pid | name | totstock | totsales 
1 | pencil | 9  | 3 
2 | paper | NULL | NULL 

Answer 1

SELECT p.pid,p.product_name,totstock, totsale 
FROM tblproducts p 
LEFT JOIN (Select pid, Sum(qty) as totstock from tblstocks group by pid) s ON s.pid=p.pid 
LEFT JOIN (Select pid, Sum(qty) as totsale from tbls group by pid) sl ON sl.pid=p.pid 

Sql Fiddle Demo

Answer 2

입니다

p.product_name (으)로 그룹을 사용해보십시오. 제 생각에는 문제가 해결 될 것입니다.