Its sum
value by each order u will need. According to your original question orderamount <100
then add 5
WITH cte
AS (
SELECT OrderID
,OrderDate
,Customer
,ProductAmount
,sum(orderamount) orderamount
FROM mytable
GROUP BY OrderID
,OrderDate
,Customer
,ProductAmount
)
SELECT OrderID
,OrderDate
,Customer
,ProductAmount
,CASE
WHEN orderamount < 100
THEN orderamount + 5
ELSE orderamount
END Orderamount
FROM cte