查询SQL以获取库存数量

Question

I have this db table

ORDER_DATE PRODUCT_ID  QTY ACTION LOT
2017-03-01    A         5    A     01
2017-03-02    A         3    R     01
2017-03-02    A         4    A     02
2017-03-03    B         3    A     C1
2017-03-04    B         3    A     C2

I have a product (PRODUCT_ID) and I can Add or Remove (Action) a certain quantity (QTY) in the various lots (LOT).

I would like to create a SQL Query for knowing the total amount of a product in stock for each lot.

Thanks for your support.

Answer 1

If R is remove, it will be negative?

Try a conditional sum

select Product_ID, Lot, 
       sum(case when action = 'R' then -1 else 1 end * QTY) as Stock
from MyTable
group by Product_ID, Lot