Re: Finding orphan records

I would use an outer join and check only those null-value records in the
right table with id's referencing table A

Sample query:

select a.*,b.* from a
left outer join b on a.id = b.a_id -- assuming a_id is my referencing
column to a
where b.id is null;

This will yield all columns in table a which has a null value on table b

This is just from the top of my head, just a concept, I might have some
syntax error.

-----Original Message-----
From: pgsql-general-owner(at)postgresql(dot)org
[mailto:pgsql-general-owner(at)postgresql(dot)org] On Behalf Of Wes
Sent: Wednesday, January 11, 2006 11:51 PM
To: Postgresql-General
Subject: [GENERAL] Finding orphan records

I'm trying to find/delete all records in table A that are no longer
referenced by tables B or C. There are about 4 million records in table A,
and several hundred million in tables B and C.

Is there something more efficient than:

select address_key, address from addresses where ( not exists(select 1 from
B where BField=addresses.address_key limit 1) ) and ( not exists(select 1
from C where CField=addresses.address_key limit 1) )

Of course, all fields above are indexed.

There are foreign key references in B and C to A. Is there some way to
safely leverage that?

Wes

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