On 05/29/07 09:48, Robert James wrote:
I'd like to be able to detect if a record has associations. I don't want
to actually delete it, just know if it could be deleted. (This is to
build an intelligent menu on a GUI)
Are you wanting to know this in a generic way or for a specific
database?
P.S. - Please don't top-post.
On 5/29/07, *Albe Laurenz* <[EMAIL PROTECTED]
<mailto:[EMAIL PROTECTED]>> wrote:
> Is there anyway to know if a DELETE will violate an FK
> without actually trying it?
I don't know what you mean by 'without trying it', but does the
following answer your question?
CREATE TABLE a (id integer PRIMARY KEY);
CREATE TABLE b (id integer PRIMARY KEY,
a_id integer NOT NULL CONSTRAINT b_fkey REFERENCES a(id));
INSERT INTO a (id) VALUES (1);
INSERT INTO b (id, a_id) VALUES (42, 1);
DELETE FROM a WHERE id=1;
ERROR: update or delete on table "a" violates foreign key constraint
"b_fkey" on table "b"
DETAIL: Key (id)=(1) is still referenced from table "b".
Yours,
Laurenz Albe
--
Ron Johnson, Jr.
Jefferson LA USA
Give a man a fish, and he eats for a day.
Hit him with a fish, and he goes away for good!
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