Re: DELETE using an outer join

On Thu, Jul 19, 2012 at 4:43 PM, Thomas Kellerer <spam_eater(at)gmx(dot)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

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