Putting pre-update values into another table with a trigger - sql

Question

I've created a table called ProductsAudit that is meant to hold values from the MyGuitarShop Products table after they have been updated with a trigger, but I can't seem to get it to work. I'm doing this in SQL Server.
So what I need to happen is when Products is updated, it stores the old value in to the ProductsAudit table.
CREATE TABLE ProductsAudit
(
AuditID int NOT NULL,
CategoryID int,
ProductCode varchar(10) NOT NULL,
ProductName varchar(255) NOT NULL,
ListPrice money NOT NULL,
DiscountPercent money NOT NULL,
DateUpdated datetime
PRIMARY KEY (AuditID)
FOREIGN KEY (CategoryID) REFERENCES Categories(CategoryID)
)
CREATE TRIGGER Products_UPDATE2
ON Products
AFTER UPDATE
AS
BEGIN;
ROLLBACK TRAN
INSERT INTO ProductsAudit
SELECT CategoryID, ProductCode, ProductName, ListPrice, DiscountPercent
FROM Deleted
WHERE CategoryID = (SELECT CategoryID FROM Inserted);
PRINT 'Old data sent to ProductsAudit'
END;
UPDATE Products
SET ListPrice = 79.43
WHERE ProductID = 3;

Answer 1

CREATE TABLE ProductsAudit
(
AuditID int NOT NULL IDENTITY(1,1),
CategoryID int,
ProductCode varchar(10) NOT NULL,
ProductName varchar(255) NOT NULL,
ListPrice money NOT NULL,
DiscountPercent money NOT NULL,
DateUpdated datetime DEFAULT (GETDATE()),
PRIMARY KEY (AuditID),
FOREIGN KEY (CategoryID) REFERENCES Categories(CategoryID)
)
CREATE TRIGGER Products_UPDATE2
ON Products
AFTER UPDATE
AS
BEGIN;
INSERT INTO ProductsAudit (CategoryID, ProductCode, ProductName, ListPrice, DiscountPercent, DateUpdated)
SELECT
d.CategoryID
,d.ProductCode
,d.ProductName
,d.ListPrice
,d.DiscountPercent
,DateUpdated = GETDATE() -- may consider adding default to the table to handle this part
FROM
deleted d
LEFT JOIN inserted i
ON d.CategoryID= i.CategoryID --is this the Product PrimaryKey Column?
WHERE
ISNULL(d.CategoryID,-1) <> ISNULL(i.CategoryID,-1)
OR ISNULL(d.ProductCode,'') <> ISNULL(i.ProductCode,'')
OR ISNULL(d.ProductName,'') <> ISNULL(i.ProductName,'')
OR ISNULL(d.ListPrice,-1) <> ISNULL(i.ListPrice,-1)
OR ISNULL(d.DiscountPercent,-1000) <> ISNULL(i.DiscountPercent,-1000)
PRINT 'Old data sent to ProductsAudit'
END;
UPDATE Products
SET ListPrice = 79.43
WHERE ProductID = 3;
So you seem to have a few issues going on, and I will see if I can walk you through them and 1 way of fixing. First, you say you want ProductAudit to hold values "AFTER" they have been updated but your code and the term Audit suggests you want to store the OLD values (deleted) into an Audit Table not the new values so that is the assumption I worked from.
2 main issues with the code you showed.
ROLLBACK TRAN - this is sort of like an undo button that would roll back all statements in the transactions which could be more than just the update you are wanting to track. This would mean your data wouldn't actually get updated.
(SELECT CategoryId FROM Inserted) - Triggers are evaluated on a set based operation NOT a scalar value so the table inserted would have more than 1 CateogryId if more than 1 row is updated. So it would have picked the last row in the data set and only that row would have been inserted into your Audit Table.
Note you can use the deleted and the inserted tables to get to the information you want. technically you only need the deleted if you want to store a record no matter what. I am showing how to use both to detect if there was actually a change to the record and then only log if there was one.