How to use the physical location of rows (ROWID) in a DELETE statement

Question

I have a table that has a lot of duplicated rows and no primary key.
I want to remove just the duplicated records, but when I try to do this it would remove all peers.

Answer 1

Simplify this by one query level:

DELETE FROM table_name
WHERE  ctid NOT IN (
   SELECT min(ctid)
   FROM   table_name
   GROUP  BY $other_columns);

.. where duplicates are defined by equality in $other_columns.
There is no need to include columns from the GROUP BY clause in the SELECT list, so you don't need another subquery.

ctid in the current manual.