SQL表LEFT OUTER联接查询

Question

What's the solution for attached image? How to remove null?

ClosingQty column should reflect the value purchase-sale, but its reflecting null value

Answer 1

The reason is that NULL is not the same as 0. Try this:

P.Quantity-COALESCE(S.Quantity,0) AS ClosingQty

See here: http://www.w3schools.com/sql/sql_isnull.asp

Answer 2

Your solution is failing as S.QUANTITY is NULL, so any arithmetic on it will result in a NULL answer. You will need to check for null, and replace with a valid number, for example 0.

The following should work:

ISNULL(P.QUANTITY,0) - ISNULL(S.QUANTITY, 0) AS ClosingQty

The real question, though, is why is S.QUANTITY null in the first place?