Shaul Dar <shauldar@xxxxxxxxx> writes: > I assume this will work but will take a long time: > DELETE * FROM T1 where T1.PK NOT IN > (SELECT T1.PK FROM T1, T2 where T1.PK = T2.FK) Well, yeah, but it's unnecessarily inefficient --- why not just DELETE FROM T1 where T1.PK NOT IN (SELECT T2.FK FROM T2) However, that still won't be tremendously fast unless the subselect fits in work_mem. As of 8.4 this variant should be reasonable: DELETE FROM T1 where NOT EXISTS (SELECT 1 FROM T2 where T1.PK = T2.FK) Pre-8.4 you should resort to the "left join where is null" trick, but there's no need to be so obscure as of 8.4. regards, tom lane -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
