Question

I have a table

OrderID   Qty    ShopID
-----------------------
1         50     10
1         50     11
2         10     15
2         10     18

The person ordered the same order at different shops (they will later decide which one will supply it), but I must only show one qty per order, please help setting the qty = 0 where the orderid is the same and shopid > min(shopID)

e.g.

OrderID   Qty    ShopID
-----------------------
1         50     10
1         0      11
2         10     15
2         0      18 

This is just an example of the real world problem pls

Answer 1

You can try something like this:

;WITH CTE AS
(
    SELECT 
        OrderID, Qty, ShopID,
        RowNum = ROW_NUMBER() OVER (PARTITION BY OrderID ORDER BY ShopID DESC)
    FROM
        dbo.YourOrderTableHere
)
SELECT
    OrderID,
    OrderedQty = CASE RowNum    
                    WHEN 1 THEN Qty ELSE 0 
                 END,
    ShopID
FROM CTE    

Basically, I “partition” the data by OrderID – so each row within a given order gets assigned a consecutive RowNum.

In the select from the CTE (Common Table Expression), I return the quantity as stored in the table for the order with RowNum = 1, and I suppress that quantity and return 0 instead for all additional rows for that same OrderID.

This gives me an output of: