联合所有结果表

Question

我只想在我的3桌中得到结果。首先，它将汇总每个商品代码的数量。然后根据我的公式输出结果。

SUM(table 1)
itemcode   qty   date
001        20   06-17
002        20   06-17
001        10   06-18


+(add) of

SUM(table 2)
itemcode   qty  date
001        10   06-17
002        40   06-17
001        5    06-18

-(subtract) of 

table 3
itemcode   qty date
001        5   06-17
002        5   06-17
002        5   06-18

结果：

itemcode   qty
001        40
002        50

Answer 1

使用以下查询

select t.itemcode as itemcode,sum(t.qty) as qty
from ( 
select itemcode,qty from table1
union all
select itemcode,qty from table2
union all
select itemcode,(qty * -1) from table3) as t
group by t.itemcode

Answer 2

这里你去:) http://www.sqlfiddle.com/#!9/ce1d25/1/0

select TsumaTotal.itemcode, suma-resta from
(select Tsuma.itemcode,SUM(Tsuma.suma) as suma from
(select tb1.itemcode, SUM(tb1.qty) as suma from Table1 as tb1 group by tb1.itemcode
UNION
select tb2.itemcode, SUM(tb2.qty) as suma from Table2 as tb2 group by tb2.itemcode) as Tsuma
group by Tsuma.itemcode) as TsumaTotal right join 
(select tb1.itemcode, SUM(tb1.qty) as resta from Table3 as tb1 group by tb1.itemcode) as Tresta
on TsumaTotal.itemcode = Tresta.itemcode;