mysql - SQL SELECT SUM 从两个表和分组依据

Question

我有两个表(PO 和 GRN)。我想得到:[这就是我正在做的:][1] http://sqlfiddle.com/#!9/db000/2

我得到了这些结果(错误的 po_qty 、 GRN_qty 和 GRN_balance )。

我期待的是:

| Item | PONO | po_qty | GRN_qty | GRN_balance |
|------|------|--------|---------|-------------|
|    A |  po1 |     70 |      65 |           5 |
|    B |  po1 |     50 |       0 |          50 |
|    C |  po2 |     10 |       5 |           5 |
|    D |  po3 |     20 |       0 |          20 |
|    A |  po4 |     15 |      10 |           5 |

Answer 1

这里有一个方法

select 
p.Item,
p.PONO,
sum(p.Qty) as po_qty,
coalesce(g.GRN_qty,0) ,
sum(p.Qty) - coalesce(g.GRN_qty,0) as GRN_balance
from PO p
left join (
  select PONO,Item,sum(Qty) as GRN_qty from GRN
  group by PONO,Item
)g
on g.PONO = p.PONO and g.Item = p.Item
group by p.Item,p.PONO
order by p.PONO

http://sqlfiddle.com/#!9/db000/30