Not converting anything but get error: "Conversion failed converting varchar value 'X' to data type int"

Question

I have created the following trigger that fires instead of an UPDATE statement and copies the altered data over to an Audit table before proceeding with the requested UPDATE. After doing so, I wrote a simple UPDATE statement for testing:
UPDATE Products
SET ProductCode = 'XYZ 2014', ProductName = 'Special Edition Tamborine', ListPrice = 74.99, DiscountPercent = .5
WHERE ProductID = 28;
When I run this, I get the following message:
Msg 245, Level 16, State 1, Procedure Products_UPDATE, Line 14
Conversion failed when converting the varchar value 'X' to data type int.
Here is my trigger:
IF OBJECT_ID('Products_UPDATE') IS NOT NULL
DROP TRIGGER Products_UPDATE; -- LINE 14
GO
CREATE TRIGGER Products_UPDATE
ON Products
INSTEAD OF UPDATE
AS
DECLARE @ProductID int, @CategoryID int, @ProductCode varchar, @ProductName varchar,
@Description varchar, @ListPrice money, @DiscountPercent money, @DateUpdated datetime
BEGIN
SELECT @ProductID = ProductID, @CategoryID = CategoryID, @ProductCode = ProductCode,
@ProductName = ProductName, @Description = Description, @ListPrice = ListPrice,
@DiscountPercent = DiscountPercent, @DateUpdated = GetDate()
FROM deleted;
INSERT INTO ProductsAudit
VALUES (@ProductCode, @CategoryID, @ProductCode, @ProductName, @ListPrice,
@DiscountPercent, @DateUpdated);
SELECT @ProductID = ProductID, @CategoryID = CategoryID, @ProductCode = ProductCode,
@ProductName = ProductName, @Description = Description, @ListPrice = ListPrice,
@DiscountPercent = DiscountPercent, @DateUpdated = GetDate()
FROM inserted;
UPDATE Products
SET CategoryID = @CategoryID, ProductCode = @ProductCode,
ProductName = @ProductName, Description = @Description,
ListPrice = @ListPrice, DiscountPercent = @DiscountPercent
WHERE ProductID = (SELECT ProductID FROM inserted)
END
I am confused a bit by (1) the location of the error and (2) the reason. I have looked over my defined data types and they all match.
Could someone offer a second set of eyes on the above and perhaps guide me towards a solution?
Thank you.

Answer 1

This is an issue in this trigger. It will work for single record updates alone. Also for your requirement you dont need a INSTEAD OF TRIGGER at all.
You just need this
IF OBJECT_ID('Products_UPDATE') IS NOT NULL
DROP TRIGGER Products_UPDATE;
GO
CREATE TRIGGER Products_UPDATE
ON Products
AFTER UPDATE
AS
BEGIN
INSERT INTO ProductsAudit
SELECT ProductID,
CategoryID,
ProductCode,
ProductName,
ListPrice,
DiscountPercent,
GetDate()
FROM deleted;
END
Now, in your original posted code there was a typo ie you repeated the column ProductCode twice
I think one should be ProductID which is why you got error due to data mismatch (ProductID is int and ProductName is varchar)
see below modified version of your original code
IF OBJECT_ID('Products_UPDATE') IS NOT NULL
DROP TRIGGER Products_UPDATE; -- LINE 14
GO
CREATE TRIGGER Products_UPDATE
ON Products
INSTEAD OF UPDATE
AS
DECLARE @ProductID int, @CategoryID int, @ProductCode varchar, @ProductName varchar,
@Description varchar, @ListPrice money, @DiscountPercent money, @DateUpdated datetime
BEGIN
SELECT @ProductID = ProductID, @CategoryID = CategoryID, @ProductCode = ProductCode,
@ProductName = ProductName, @Description = Description, @ListPrice = ListPrice,
@DiscountPercent = DiscountPercent, @DateUpdated = GetDate()
FROM deleted;
INSERT INTO ProductsAudit
VALUES (@ProductID, @CategoryID, @ProductCode, @ProductName, @ListPrice,
@DiscountPercent, @DateUpdated);
SELECT @ProductID = ProductID, @CategoryID = CategoryID, @ProductCode = ProductCode,
@ProductName = ProductName, @Description = Description, @ListPrice = ListPrice,
@DiscountPercent = DiscountPercent, @DateUpdated = GetDate()
FROM inserted;
UPDATE Products
SET CategoryID = @CategoryID, ProductCode = @ProductCode,
ProductName = @ProductName, Description = @Description,
ListPrice = @ListPrice, DiscountPercent = @DiscountPercent
WHERE ProductID = (SELECT ProductID FROM inserted)
END
I would prefer doing it as former way though
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