连接两个数据表后的分组汇总问题
请大虾看看“结存减包装出库”数据为何不对：

SELECT s.代码, s.简化名称,
SUM(s.入库-s.出库) AS 结存
FROM VScdj s
WHERE s.代码= '1304-0200-03-0100 '
GROUP BY s.代码, s.简化名称


SELECT c.代码, m.简化名称,
SUM(c.出库) AS 包装出库
FROM 成品出入库单 c LEFT JOIN 材料代码 m ON (c.代码=m.代码)
WHERE c.工序= '包装 ' AND c.代码= '1304-0200-03-0100 '
GROUP BY c.代码, m.简化名称


SELECT s.代码, s.简化名称,
SUM(s.入库-s.出库)-SUM(c.出库) AS 结存减包装出库
FROM VScdj s INNER JOIN 成品出入库单 c ON (c.代码=s.代码 AND c.工序= '包装 ')
WHERE s.代码= '1304-0200-03-0100 '
GROUP BY s.代码, s.简化名称


（所影响的行数为 1 行）

代码简化名称结存
--------------------------
1304-0200-03-0100 AgNi(10)-ASE-W 5058.850


（所影响的行数为 1 行）

代码简化名称包装出库
--------------------------
1304-0200-03-0100 AgNi(10)-ASE-W 8419.072

（所影响的行数为 1 行）

代码简化名称结存减包装出库
--------------------------
1304-0200-03-0100 AgNi(10)-ASE-W -5282775.106


[解决办法]
select s.代码, s.简化名称, sum(s.入库-s.出库) - sum(c.出库) as 结存减包装出库
from VScdj s inner join 成品出入库单 c on s.代码 = c.代码
inner join 材料代码 m on c.代码 = m.代码
where s.代码= '1304-0200-03-0100 ' and c.工序= '包装 '
group by s.代码, s.简化名称

行吧
[解决办法]
--看看例子，你就容易理解了。

--有，出的是
Select A.* From
(Select 1 As ID) A
Inner Join
(Select 1 As ID
Union All
Select 1
Union All
Select 2) B
On A.Id = B.ID


--但是B中如果也有ID1的，果就出重了
Select A.* From
(Select 1 As ID
Union All
Select 1) A
Inner Join
(Select 1 As ID
Union All
Select 1
Union All
Select 2) B
On A.Id = B.ID