在我的情况下，如何使用SQL Server进行分组？

Question

I wants to calculate sum of quantity based on Quantity value

For Example

ItemNo    Quantity
------------------
111       5
111       -2
111       3
112       10

I want to do grouping by ItemNo and calculate like below

ItemNo    Quantity    Positive   Negative
-----------------------------------------
111       6            8           -2
112       10           10          0

I tried like this

SELECT
    ItemNo,
    Sum(Quantity),
    Case when Quantity >= 0 then sum(quantity) else 0 end POSITIVE,
    Case when Quantity < 0 then sum(quantity) else 0 end Negative
From
    Sales
Group By
    ItemNo,
    Quantity

I know this grouping is wrong. How my query should be?

thanks

Answer 1

Just put the SUM() around your CASE() statement:

SELECT
    ItemNo,
    Sum(Quantity),
    SUM(Case when Quantity >= 0 then quantity else 0 end) POSITIVE,
    SUM(Case when Quantity < 0 then quantity else 0 end) Negative
From
    Sales
Group By
    ItemNo;

Also, remove Quantity from your GROUP BY. You are aggregating quantity with a sum() so it's nonsense to GROUP BY it as well.

Answer 2

I would leave this as a comment to JNevill's answer if I had the reputation, but you would also want to give the quantity sum an alias to get the results in the question. For example: SELECT ItemNo, Sum(Quantity) Quantity, SUM(Case when Quantity >= 0 then Quantity else 0 end) Positive, SUM(Case when Quantity < 0 then Quantity else 0 end) Negative From Sales Group By ItemNo;