Hi, (this is not a real world problem, just something I'm playing around with).
Lately I had some queries of the form: select t.* from some_table t where t.id not in (select some_id from some_other_table); I could improve the performance of them drastically by changing the NOT NULL into an outer join: select t.* from some_table t left join some_other_table ot on ot.id = t.id where ot.id is null; Now I was wondering if a DELETE statement could be rewritten with the same "strategy": Something like: 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) The DELETE .. USING seems to only allow inner joins because it requires the join to be done in the WHERE clause. So I can't think of a way to turn that NOT IN from the DELETE into an outer join with a derived table. Am I right that this kind of transformation is not possible or am I missing something? Regards Thomas -- Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-sql