On Wed, Mar 23, 2011 at 4:08 PM, <tv@fuzzy.cz> wrote:
> I just want to retrieve that id 's from page_content which do not have > any entry in clause2 table.
In that case the query probably does not work (at least the query you've sent in the first post) as it will return even those IDs that have at least one other row in 'clause2' (not matching the != condition). At least that's how I understand it.
true.
So instead of this
select distinct(p.crawled_page_id)
from page_content p, clause2 c where p.crawled_page_id != c.source_id ;
you should probably do this
select distinct(p.crawled_page_id)
from page_content p left join clause2 c on (p.crawled_page_id = c.source_id) where (c.source_id is null);
I guess this will be much more efficient too.
This looks like to give expected results. Also note that the where clause "is null" is really required and is not an optional predicate.
