Hello Andras,
I did some more tests with queries like the following:
SELECT 1 WHERE EXISTS(SELECT * FROM sys.objects )
SELECT 1 WHERE EXISTS(SELECT TOP 1 * FROM sys.objects )
It seems to make no difference, regardless of the table size.
If I remember correctly, it was one of Itzik's books where I read about this behaviour but I cannot tell for sure.
Best Regards,
Chris Büttner