IF (@SalePrice * 100) / @ListPrice > 50
BEGIN
     SET @CommisionRateID = 3;

     SELECT * FROM CarDetails

     UPDATE CarDetails
     SET CommissionRateID = @CommisionRateID
     FROM CarDetails
     WHERE CarID = (@i + 1)
END

CREATE PROC spAssignCommissionRate
AS
BEGIN
    UPDATE CarDetails
    SET CommissionRateID = CASE WHEN (SalePrice * 100) / ListPrice > 50 THEN 3
                                 WHEN (SalePrice * 100) / ListPrice > 30 THEN 2
                                 ELSE 1
                            END
    WHERE CommissionRateID IS NULL
END