Question

I have table called Table A and I have created a trigger that handles INSERTS, UPDATES, DELETES. Now in order to process my next steps, I want to know what DML action has taken place. How do I know whether an Update/Insert/Delete has taken place.

Your thoughts, feedback is much appreciated!

Answer 1

Inside the trigger, you have two special tables at your disposal: INSERTED and DELETED. If a row exists only in the INSERTED table, then an INSERT operation occurred. Likewise, if a row exists only in the DELETED table, then a DELETE operation occurred. If the row exists in both tables, then an UPDATE occurred and the INSERTED table holds the new values while the DELETED table holds the old values.

INSERTed Rows:

SELECT i.*
    FROM INSERTED i
        LEFT JOIN DELETED d
            ON i.PrimaryKey = d.PrimaryKey
    WHERE d.PrimaryKey IS NULL

DELETEd Rows:

SELECT d.*
    FROM DELETED d
        LEFT JOIN INSERTED i
            ON d.PrimaryKey = i.PrimaryKey
    WHERE i.PrimaryKey IS NULL

UPDATEd Rows:

SELECT *
    FROM INSERTED i
        INNER JOIN DELETED d
            ON i.PrimaryKey = d.PrimaryKey