Sorry I messed up the first query, here is the corrected version
SELECT a.*
FROM tablea a
WHERE a.iPKID NOT IN (SELECT b.iTableALinkID FROM tableb b)
...

--- In firebird-support@yahoogroups.com, "venussoftop" <venussoftop@...> wrote:
>
> Hi all
>
> I have tables that can allow me to filter data like this:
> SELECT a.*
> FROM tablea a
> WHERE a.iTableBLinkID NOT IN (SELECT b.iPKID FROM tableb b)
> ...
> these tables will grow over the years with more and more records cancelling each other out, so there really will be only few tens of records which do not have a corresponding iTableBLinkID records at any given point of time
>
> Or should I introduce a flag in tablea, something like iClosed SMALLINT which is default zero but set to 1 programatically so the same result could be got like
> SELECT a.*
> FROM tablea a
> WHERE a.iClosed = 0
> ...
>
> Which is more efficient from SQL point of view?
>
> Please advise
>
> Thanks and regards
> Bhavbhuti
>