On Thu, Jul 19, 2012 at 4:43 PM, Thomas Kellerer <spam_eater@gmx.net> wrote:
> delete from some_table
> where id not in (select min(id)
> from some_table
> group by col1, col2
> having count(*) > 1);
>
> (It's the usual - at least for me - "get rid of duplicates" statement)
If you want to remove duplicates you can do it this way.
DELETE FROM some_table USING some_table AS s
WHERE some_table.col1 = s.col1 AND some_table.col2 = s.col2 AND some_table.id < s.id;
The query plan should be better than one with the sub query and NOT IN.
ps. May be this example is worth to append to the documentation?
--
Sergey Konoplev
a database architect, software developer at PostgreSQL-Consulting.com
http://www.postgresql-consulting.com
Jabber: gray.ru@gmail.com Skype: gray-hemp Phone: +79160686204
