To simplify things, lets say I have a models StockIOLog.
class StockIOLog(models.Model):
pid = models.IntegerField()
name= models.CharField(max_length=50)
type= models.IntegerField()
stock = models.IntegerField()
It contains following data:
pid | name | batch | type | quantity
------------------------------------------------
1 | Napa | AB | 0 | 100
------------------------------------------------
1 | Napa | AA | 0 | 100
------------------------------------------------
2 | Amod | AA | 0 | 100
------------------------------------------------
2 | Amod | CA | 0 | 100
------------------------------------------------
1 | Napa | AB | 1 | 10
------------------------------------------------
1 | Napa | AB | 1 | 5
------------------------------------------------
1 | Napa | AA | 1 | 20
------------------------------------------------
2 | Amod | AA | 1 | 10
------------------------------------------------
2 | Amod | AA | 1 | 50
------------------------------------------------
2 | Amod | CA | 1 | 5
------------------------------------------------
2 | Amod | CA | 1 | 15
type 0 means product was purchased, type 1 means product was consumed, Now I want to calculate total stock of every product batch-wise.
By running following SQL query
SELECT pid, name, batch, SUM(in) - SUM(out) as stock FROM (
SELECT pid, name, type SUM(quantity) as in, 0 as out from `qset` WHERE type=0 GROUP BY pid,type,batch as a
UNION
SELECT pid, name, type 0 as in, SUM(quantity) as out from `qset` WHERE type=1 GROUP BY pid,type,batch as b
) ac table_a
I get following queryset
pid | name | batch | stock
-----------------------------------
1 | Napa | AB | 85
-----------------------------------
1 | Napa | AA | 80
-----------------------------------
2 | Amod | AA | 40
-----------------------------------
2 | Amod | CA | 80
How to do similar things in django ORM?