Sql-server – How to reference only affected rows in AFTER UPDATE trigger

row-modification-timesql serversql-server-2012t-sqltrigger

I have this table:

enter image description here

And I'm trying to create an update trigger which will update last_updated_on = GETDATE() and last_updated_by = SYSTEM_USER columns whenever an update is performed on step_number or step_name column.

I started creating it by 

ALTER TRIGGER tr_app_bread_crumbs_afterupdate
ON [dbo].[app_bread_crumbs]
AFTER UPDATE
AS
BEGIN 
    UPDATE [dbo].[app_bread_crumbs]
    SET last_updated_by = SYSTEM_USER,
    last_updated_on = GETDATE()
END

But this will update all rows at once. I'm trying to figure out how to specify to only update last_updated_on and last_updated_by by the trigger for the specific row where updates are being made.

For example if they update:

UPDATE [dbo].[app_bread_crumbs]
    SET step_name = 'DAMAGE' WHERE step_number = 1

Only first row should be updated by the trigger

Best Answer

Use the inserted table, which is a special table available inside triggers containing the rows that will be updated/inserted into the table.

ALTER TRIGGER tr_app_bread_crumbs_afterupdate
ON [dbo].[app_bread_crumbs]
AFTER UPDATE
AS
BEGIN 
    UPDATE [dbo].[app_bread_crumbs]
    SET last_updated_by = SYSTEM_USER,
    last_updated_on = GETDATE()
    FROM dbo.app_bread_crumbs abc
    WHERE EXISTS (SELECT 1 FROM inserted i WHERE i.id = abc.id);
END
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