tsql trigger behaves abnormally - tsql

Question

I have a trigger which is as follows:
ALTER TRIGGER [trigger_CATEGORY_VALUE_ID] ON [dbo].[tblA]
FOR UPDATE
AS
SET NOCOUNT ON
IF ( UPDATE([CATEGORY_VALUE_ID]))
BEGIN
INSERT INTO [dbo].[htblB]
( ID
, CATEGORY_VALUE_ID
, STATUS_END_DATE
, STATUS_END_DATE_SOURCE)
SELECT
t.ID
, t.CATEGORY_VALUE_ID
, GETDATE()
, t.UPDATE_SOURCE
FROM [dbo].[tblCAPITATION] t
INNER JOIN inserted ins
ON t.CATEGORY_VALUE_ID = ins.CATEGORY_VALUE_ID
END
What it needs to do is insert a new row in htblB when the column CATEGORY_VALUE_ID is updated. It works fine if only one row is updated. But if it has multiple row updates, then 2 to the power number of rows updated amount of new rows are inserted in htblB.
UPDATE dbo.tblCAPITATION
SET CAPITATION_STATUS_CATEGORY_VALUE_ID = '80574', UPDATE_SOURCE = 'TEST3'
WHERE CAPITATION_ID = 2 OR CAPITATION_ID = 3
This statement will insert 4 new rows to htblB instead of 2.
May you please shed some light on why this is hapening and how to prevent it?
Thanks!

Answer 1

I'm going to assume that ID is the primary key, if so then you should be joining inserted on ID not category_value_id
ALTER TRIGGER [trigger_CATEGORY_VALUE_ID] ON [dbo].[tblA]
FOR UPDATE
AS
SET NOCOUNT ON
IF ( UPDATE([CATEGORY_VALUE_ID]))
BEGIN
INSERT INTO [dbo].[htblB]
( ID
, CATEGORY_VALUE_ID
, STATUS_END_DATE
, STATUS_END_DATE_SOURCE)
SELECT
t.ID
, t.CATEGORY_VALUE_ID
, GETDATE()
, t.UPDATE_SOURCE
FROM [dbo].[tblCAPITATION] t
INNER JOIN inserted ins
ON t.ID = ins.ID
END