Create a history trigger SQL Server 2012 - sql-server

Question

I have no idea how to create this history trigger.
Imagine that we would like to store a history of price changes for each item. To do so, we would first need to create an Item_price_history table that stores at a minimum a reference to the item, its old price, 
its new price, and the date of the change. We could then define a trigger on the Item 
table that updates the Item_price_history table whenever an item price is updated. 
I have created two tables as below:
CREATE TABLE ITEM(
item_id DECIMAL(10) NOT NULL,
description VARCHAR(30),
price DECIMAL(10),
PRIMARY KEY (item_id));
CREATE TABLE Item_price_history (
history_id DECIMAL(10) NOT NULL,
item_id DECIMAL(10) NOT NULL,
old_price DECIMAL(10,2),
new_price DECIMAL(10,2),
date_of_change DATE,
PRIMARY KEY (HISTORY_ID),
FOREIGN KEY (ITEM_ID) REFERENCES item);

Answer 1

Here is the trigger:
CREATE TRIGGER trHistory ON dbo.ITEM
FOR UPDATE --only for update
AS
BEGIN
IF UPDATE(price) --if price is really updated and not the other columns
BEGIN
INSERT INTO dbo.Item_price_history(item_id, old_price, new_price, date_of_change)
SELECT d.item_id, d.price, i.price, GETDATE()
FROM Deleted d
JOIN Inserted i ON d.item_id = i.item_id
END
END

Answer 2

Try this.
CREATE TRIGGER Sample ON Item_price_history
FOR UPDATE
AS
BEGIN
DECLARE #nOldPRICE AS DECIMAL(10)
SET #nOldPRICE = (SELECT price FROM DELETED)
INSERT INTO Item_price_history (item_id, old_price, new_price, date_of_change)
SELECT item_id, #nOldPRICE, new_price, GETDATE() FROM INSERTED
END

Answer 3

For sure you can use a trigger. But why?
You can update the history table when you update the main table and keep all the business logic in one place.
I remember in old days, during a programming SQL2000 seminar that it was told:
"Avoid the use of triggers. In most cases they try to solve design problems."
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