SQL Server trigger if update() with condition - sql

Question

I have a table in SQL Server that has 3 columns: ID, NAME, VALUE.
This table has 2 rows with ID=1 and ID=2.
(The value of ID doesn't change).
Every moment of time the value of column VALUE changes. Every time the column VALUE changes, I want to insert this updated value into a table (Device1 for ID=1, Device1 for ID=2).
I created a trigger for updating as if update(VALUE) begin...but it doesn't do the work.
Is there a way to add a condition in if update(VALUE) to work in each row
I used this query
Create Trigger insertIntoDevices
On ITEMS
For Update
As
If Update(VALUE)
Begin
Insert Into table device1
Where ID = 1
Insert Into table device2
Where ID = 2
End
With this query each update in column VALUE inserts VALUE into device1 and device1 and that duplicates values in my tables device1 and device2.

Answer 1

Table creation on the below ;
CREATE TABLE TestTable(
ID INT IDENTITY(1,1),
Name VARCHAR(5),
VALUE NVARCHAR(50)
)
GO
CREATE TABLE device1(
VALUE NVARCHAR(50)
)
GO
CREATE TABLE device2(
VALUE NVARCHAR(50)
)
GO
Insertion for ID=1 and ID=2
GO
INSERT INTO TestTable(Name,Value)
VALUES('Test1','test1'),('TEST2','test2')
Firstly,To find new values for each row you can use 'inserted' but it can be include non-changed data. For example: ID =1,Name='test1' and VALUE='test1' and updation of name column will be also included in inserted.
Secondly,To find old values for each row you can use 'deleted'.
After that we find the values that only includes updation for VALUE.
To Sump Up,
Finding Inserted rows and deleted rows will give us the result of each rows new and old values. We used intersection (INNER JOIN ) to find only changed values.
CREATE TRIGGER [dbo].[insertIntoDevices]
ON [dbo].[TestTable]
AFTER UPDATE
AS
BEGIN
DECLARE #InsertedTable table (
InsertedID INT,
InsertedName VARCHAR(5),
InsertedVALUE NVARCHAR(50)
)
DECLARE #DeletedTable table (
DeletedID INT,
DeletedName VARCHAR(5),
DeletedVALUE NVARCHAR(50)
)
INSERT INTO #InsertedTable(InsertedID,InsertedName,InsertedVALUE)
SELECT ID,[Name],[Value] FROM inserted;
INSERT INTO #DeletedTable(DeletedID,DeletedName,DeletedVALUE)
SELECT ID,Name,Value FROM deleted;
INSERT INTO device1(VALUE)
SELECT UpdatedValue = it.InsertedVALUE
FROM #InsertedTable as it
INNER JOIN #DeletedTable as dt ON it.InsertedID = dt.DeletedID AND ISNULL(dt.DeletedVALUE,'') <> ISNULL(it.InsertedVALUE,'')
WHERE it.InsertedID = 1
INSERT INTO device2(VALUE)
SELECT UpdatedValue = it.InsertedVALUE
FROM #InsertedTable as it
INNER JOIN #DeletedTable as dt ON it.InsertedID = dt.DeletedID AND ISNULL(dt.DeletedVALUE,'') <> ISNULL(it.InsertedVALUE,'')
WHERE it.InsertedID = 2
END
To test I used the updation queries on the below;
--Example 1
UPDATE TestTable
SET Value='selam'
WHERE ID = 1
--Example 2
UPDATE TestTable
SET Value='hi'
WHERE ID = 2