Question

I have been using a TSQL trigger under the assumption that the inserted table always contains records for an insert or update and the deleted table always contains records for updates (I am ignoring deletes).

Here is the related MSDN article:

http://msdn.microsoft.com/en-us/library/ms191300.aspx

However, I have encountered situations where both inserted and deleted are empty. Here is a test trigger I have been using.

CREATE TRIGGER [dbo].[InsertUpdateTest] ON [dbo].[Test] 
AFTER INSERT, UPDATE 
AS
    DECLARE @countInserted INT
    DECLARE @countDelete INT

    SET @countInsert = (SELECT COUNT(*) FROM INSERTED)
    SET @countDeleted = (SELECT COUNT(*) FROM DELETED)

    IF (@countInserted = 0 AND @countDelete = 0)
    BEGIN
        print 'Inserted and deleted are both empty'
    END

Under what conditions does this occur?

Answer 1

Answering my own question. This occurs when an update statement on the triggered table doesn’t update any rows. The trigger still fires but with empty inserted and deleted tables. For example:

UPDATE Test Set somefield=0 WHERE id='Values does not exist'