CREATE TRIGGER discountCustomer
ON
Orders
FOR INSERT
AS BEGIN
DECLARE @deliveredOrders INT, @custID INT
SELECT @custID = Order_customer FROM INSERTED
EXEC @deliveredOrders = numberOfCompletedOrders @custID
IF @deliveredOrders > 10 AND @deliveredOrders < 20
BEGIN
    IF (SELECT COUNT(Customer_id) FROM Customer_discount WHERE Customer_id = @custID) < 0
    BEGIN
    INSERT INTO Customer_discount VALUES (@custID, 10)
    END
END
IF @deliveredOrders > 20
BEGIN
    IF (SELECT Discount_percent FROM Customer_discount WHERE Customer_id = @custID) != 20
    BEGIN
    UPDATE Customer_discount SET Discount_percent = 20 WHERE Customer_id = @custID
    END
END
END