Use Join , Sum and Group by in a query with three table - join

Question

I have three tables:
**OBTable**
Product obquantity obrate obTotalAmmount
Matadoor Pen 100 8 800
Matadoor Pen 1000 4 4000
**PurchaseTable**
pProduct Pquantity pRate SaleRate pTotalAmmount
Matadoor Pen 150 4 5 600
Matadoor Pen 400 8 10 3200
Matadoor Pen 1500 9 10 13500
**SaleTable**
sProduct sQuantity sRate sTotalAmmount
Matadoor Pen 100 10 1000
Matadoor Pen 350 10 3500
Matadoor Pen 1350 10 13500
My query:
SELECT
Product,
SUM(obQuantity) AS obQuantity,
SUM(obTotalAmmount)/SUM(obQuantity) AS obRate,
SUM(obTotalAmmount) AS obTotalAmmount,
pProduct,
SUM(pQuantity) AS pQuantity,
SUM(pTotalAmmount)/SUM(pQuantity) AS pRate,
SUM(pTotalAmmount) AS pTotalAmmount,
sProduct,
SUM(sQuantity) AS sQuantity,
SUM(sTotalAmmount)/SUM(sQuantity) AS sRate,
SUM(sTotalAmmount) as sTotalAmmount,
Sum(obQuantity) +SUM(pquantity) -Sum(squantity) as obpsQTY,
(Sum(obTotalAmmount)+Sum(pTotalAmmount)-sum(sTotalAmmount))/(Sum(obQuantity)+SUM(pQuantity)-Sum(sQuantity)) as obpsrate ,
(Sum(obTotalAmmount)+Sum(pTotalAmmount))-Sum(sTotalAmmount) as obpstotal
from OBTable
left join
PurchaseTable on OBTable.Product=PurchaseTable.pProduct
left join
Saletable on PurchaseTable.pProduct=SaleTable.sProduct
Group BY OBTable.Product,PurchaseTable.pProduct,Saletable.sProduct
It's executed answer is not correct. Plz help me and give tips to solve it.

Answer 1

You can try this code:
Select Product,
Sum(obQuantity) As obQuantity,
(SUM(obTotalAmmount)/Sum(obQuantity)) As obRate,
SUM(obTotalAmmount) as obTotalAmmount,
pQuantity,pRate,pTotalAmmount,
sQuantity ,sRate,sTotalAmmount,
(Sum(obQuantity) +pquantity) -squantity as obpsQTY,
(((SUM(obTotalAmmount)/Sum(obQuantity)))+pRate)/2 as obpsrate ,
((((SUM(obTotalAmmount)/Sum(obQuantity)))+pRate)/2)*((Sum(obQuantity) +pquantity) -squantity) as obpstotal
from OBTable
left join (
Select pProduct,Sum(pQuantity) As pQuantity ,(Sum(pTotalAmmount)/Sum(pQuantity)) As pRate,Sum(pTotalAmmount) As pTotalAmmount
from PurchaseTable
Group by PurchaseTable.pProduct
)
PurchaseTable on OBTable.Product=PurchaseTable.pProduct
left join
(
Select sProduct,Sum(sQuantity) As sQuantity ,(Sum(sTotalAmmount)/Sum(sQuantity)) As sRate,Sum(sTotalAmmount) As sTotalAmmount
from SaleTable
Group by SaleTable.sProduct
) Saletable on PurchaseTable.pProduct=SaleTable.sProduct
Group by OBTable.Product,PurchaseTable.pProduct,Saletable.sProduct,PurchaseTable.pQuantity,PurchaseTable.pRate,PurchaseTable.pTotalAmmount,Saletable.sQuantity,Saletable.sRate,Saletable.sTotalAmmount