From: ogjunk-pgjedan@yahoo.com
To: pgsql-sql@postgresql.org
Subject: Referential integrity broken (8.0.3), sub-select help
Date: Tue, 21 Mar 2006 06:58:39 -0800 (PST)
Message-ID: <20060321145839.68211.qmail@web50301.mail.yahoo.com> (raw)
Hello,
I've got 2 tables, "url" (U), and "bookmark" (B), with "bookmark" pointing to "url" via FK.
Somehow I ended up with some rows in B referencing non-existent rows in U.
This sounds super strange and dangerous to me, and it's not clear to me how/why PG let this happen.
I'm using 8.0.3.
Here are the table references I just mentioned:
Table "bookmark":
id SERIAL
CONSTRAINT pk_bookmark_id PRIMARY KEY
Table "url":
url_id INTEGER
CONSTRAINT fk_bookmark_id REFERENCES bookmark(id)
Problem #1: Strange that PG allowed this to happen. Maybe my DDL above allows this to happen and needs to be tightened? I thought the above would ensure referential integrity, but maybe I need to specify something else?
Problem #2: I'd like to find all rows in B that point to non-existent rows in U. I can do it with the following sub-select, I believe, but it's rather inefficient (EXPLAIN shows both tables would be sequentially scanned):
SELECT * FROM bookmark WHERE id NOT IN (SELECT b.id FROM bookmark b, url u WHERE b.url_id=u.id);
Is there a more efficient way to get the rows from "bookmark"?
Thanks,
Otis
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Subject: Re: Referential integrity broken (8.0.3), sub-select help
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