I think there is something else. It may be better to post the whole SP. I believe the last query is supposed to return records.

The alternative and preferrable way (more performant) to write the last query is

select E.PK from TVM.dbo.EventsLog E LEFT JOIN  tvm.dbo.FaultsLog F ON E.PK =F.fkEventsLog where F.PK IS NULL

>I have two tables EventsLog and FaultsLog, FaultsLog has a foreign key to EventsLog and I run this queries
>
>

>select EventsLog.PK from TVM.dbo.EventsLog where PK = 1095387
>
>select FaultsLog.PK, FaultsLog.fkEventsLog from TVM.dbo.FaultsLog where FaultsLog.fkEventsLog = 1095387
>
>select EventsLog.PK from TVM.dbo.EventsLog where EventsLog.PK not in (select FaultsLog.fkEventsLog from tvm.dbo.FaultsLog)
>

>
>First query returns one record, all is good.
>Second query returns no records, still good.
>Third query returns no records too?? Shouldn't I get the record for PK = 1095387?
>
>So confused...
>
>
>(By the way, this is part of a longer store procedure that was working fine until Friday, today I noticed the problem and I think I narrowed it down to a query similar to this)
>
>
>TIA,
>
>Hugo