sql server 2005错误输出

Question

我有 3 张表库存，内向，发行

股票表的列和数据:

part_no | part_name | totalqty
10100        ciol      30
112233       abc       20
123456       coper      50

内表:

part_no | qty
123456   10
123456   20
10100    20
112233   15
10100    25

问题表:

part_no | qty
112233   20
112233   15
123456   10
112233   25
10100    40
10100    20

我想要的输出:

part_no | part_name  |inwardQty |issueQty
10100      coil         45     60
112233     abc          15     60
123456     coper        30     10

以下是我编写的查询，但没有给出我想要的输出

select s.part_no,s.part_name,sum(i.qty) as inwardQty,sum(p.qty)as issueQty 
from stock s 
left join inward i on s.part_no = i.part_no
left join issue p on s.part_no = p.part_no 
group by 
    s.part_no,s.part_name

通过此查询获取以下输出:

part_no | part_name  |inwardQty |issueQty
10100      coil         90     120
112233     abc          45     60
123456     coper        30     20

Answer 1

问题是您将inward的每一行与issue的每一行进行匹配，对于他们正在处理同一部分。我认为子查询在这里最好:

select s.part_no,s.part_name,i.qty as inwardQty,p.qty as issueQty 
from stock s 
left join
    (select part_no,sum(qty) as qty from inward group by part_no) i on s.part_no = i.part_no
left join
    (select part_no,sum(qty) as qty from issue group by part_no) p on s.part_no = p.part_no 

所以现在，每个连接中只有一行(或零行)需要连接，并且您不会获得笛卡尔积。