Hi,
I have two large tables T1 and T2, such that T2 has a FK to T1 (i.e.
T2.FK -->
T1.PK, possibly multiple T2 rows may reference the same T1 row). I have deleted about 2/3 of table T2. I now want to delete all rows in T1 that are not referenced by T2, i.e. all rows in T1 that cannot join with (any row in) T2 on the condition
T2.FK =
T1.PK (the opposite of a join...)
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)
What is an
efficient way to do this?
Thanks,
-- Shaul