Hans, Yes, the IDs are enforced primary keys on all tables in the same database. Sorry that database is now being refreshed and I am waiting to see if I can reproduce this behavior again. The same queries on the source database (which is of the same version as the buggy database) works as expected. -----Original Message----- From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Hans Forbrich Sent: Wednesday, October 24, 2012 6:44 PM To: oracle-l@xxxxxxxxxxxxx Subject: Re: SQL question Exactly my point. In theory it should not, if ID is an enforced primary key. But ... One additional question, based on further posts, is: are these queries on the same DB? /Hans On 24/10/2012 2:13 PM, Rumpi Gravenstein wrote: > <snip> > Theoretically table3 should not be required in the join </snip> > > Table 3 may be acting as a filter in which case it will impact the > final count. > > Rumpi Gravenstein > -- //www.freelists.org/webpage/oracle-l -- //www.freelists.org/webpage/oracle-l