Question

I have two Tables
Let suppose A and B
Now suppose the structure of table A is Like that

id     stock
 37      1
 40      1 
 37      1 
 40      1
 37      1
 37      1

And B is like that

id     stock
37      1
37      1 
40      1

Now i want to write a query that give me sum of specific id stock in (table A – Table B) and if that id does not exist in table B then only stock from A.
So i will expect result like that

id     stock

40      1  
37      2

I thought that left join will be possible option here and i write query like that

SELECT A.id, 
    SUM(CAST(isNull(A.Stock, 0) as int) - CAST(isNull(B.Stock, 0) as int) )'Stock'
    from  A
    LEFT OUTER JOIN
    B
    ON A.id = B.id
    group by A.id

But Problem is that the above query gives desired records but wrong quantity/Stocklevel as shown below:

id     stock
37      0
40      1 

How can I resolve Stock Level issue.

Answer 1

I guess you are looking for something like this.

select A.id, A.SumA - coalesce(B.SumB, 0) as stock
from (
       select A.id, sum(A.stock) as SumA
       from A
       group by A.id
     ) as A  
  left outer join
     (
       select B.id, sum(B.stock) as SumB
       from B
       group by B.id
     ) as B
    on A.id = B.id            

Result:

id          stock
----------- -----------
37          2
40          1

SE Data