deleting the master but not the detail

am Thu, dem 17.07.2008, um 11:11:00 -0500 mailte Ismael .... folgendes:

hi
I have one of those master-detail relationships here and I need to be able
to delete the master but leave the details untouched

But the delete command doesn't let me delete the master as long as
there are details referencing it.

ON DELETE RESTRICT | NO ACTION won't let me delete the master
CASCADE | SET NULL | SET DEFAULT will modify the details

Any idea ow to do it without the use of triggers?

DROP the constraint. For example:

test=# create table master (id serial primary key, m text);
NOTICE: CREATE TABLE will create implicit sequence "master_id_seq" for serial column "master.id"
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "master_pkey" for table "master"
CREATE TABLE
test=*# insert into master (m) values ('master1');
INSERT 0 1
test=*# insert into master (m) values ('master2');
INSERT 0 1
test=*# create table slave (id int references master, s text);
CREATE TABLE
test=*# insert into slave values (1, 'slave 1');
INSERT 0 1
test=*# insert into slave values (2, 'slave 2');
INSERT 0 1
test=*# \d slave
Tabelle �public.slave�
Spalte | Typ | Attribute
--------+---------+-----------
id | integer |
s | text |
Fremdschl�ssel-Constraints:
�slave_id_fkey� FOREIGN KEY (id) REFERENCES master(id)

test=*# alter table slave drop constraint slave_id_fkey;
ALTER TABLE
test=*# drop table master;
DROP TABLE
test=*# select * from slave;
id | s
----+---------
1 | slave 1
2 | slave 2
(2 Zeilen)

test=*#

Hope that helps, Andreas
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On Thu, Jul 17, 2008 at 12:11 PM, Ismael .... <ismaelpsp@hotmail.com> wrote:

hi
I have one of those master-detail relationships here and I need to be able
to delete the master but leave the details untouched

Then remove the referential integrity constraint, since it's obviously
incompatible with your business requirements.

-Doug

On 17/07/2008 17:11, Ismael .... wrote:

ON DELETE RESTRICT | NO ACTION won't let me delete the master
CASCADE | SET NULL | SET DEFAULT will modify the details

Can you just drop the constraint that's doing the referential integrity?

Ray.

------------------------------------------------------------------
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rod@iol.ie
Galway Cathedral Recitals: http://www.galwaycathedral.org/recitals
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So is there no other way to do it but to verify the integrity using triggers
and drop the referential constraints?

Because I *still* need to verify that NEW records in the details table
direct to something that exists

ON DELETE RESTRICT | NO ACTION won't let me delete the master
CASCADE | SET NULL | SET DEFAULT will modify the details

Can you just drop the constraint that's doing the referential integrity?

Ray.

Then remove the referential integrity constraint, since it's obviously
incompatible with your business requirements.

-Doug

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On Thu, Jul 17, 2008 at 10:52 AM, Douglas McNaught <doug@mcnaught.org> wrote:

On Thu, Jul 17, 2008 at 12:11 PM, Ismael .... <ismaelpsp@hotmail.com> wrote:

hi
I have one of those master-detail relationships here and I need to be able
to delete the master but leave the details untouched

Then remove the referential integrity constraint, since it's obviously
incompatible with your business requirements.

Generally I'd agree, but it might be useful to set the child record
referencing id field to NULL in this circumstance.

It seems like 3 vs 1 so you win :)
I'll drop the constraint and verify the integrity of the new records manually

tanks

On Thu, Jul 17, 2008 at 10:52 AM, Douglas McNaught wrote:

On Thu, Jul 17, 2008 at 12:11 PM, Ismael .... wrote:

hi
I have one of those master-detail relationships here and I need to be able
to delete the master but leave the details untouched

Then remove the referential integrity constraint, since it's obviously
incompatible with your business requirements.

Generally I'd agree, but it might be useful to set the child record
referencing id field to NULL in this circumstance.

_________________________________________________________________
Tenemos lo que búscas…JUEGOS.
http://club.prodigymsn.com/

hi
I have one of those master-detail relationships here and I need to be able
to delete the master but leave the details untouched

when you create the table with an FK constraint, use the ON DELETE SET
NULL option, or SET DEFAULT. And read the docs on "CREATE TABLE":

http://www.postgresql.org/docs/8.3/static/sql-createtable.html

Then remove the referential integrity constraint, since it's obviously
incompatible with your business requirements.

Wrong. See above. Unless I misunderstand, then I apologize for the noise....

On Thu, 17 Jul 2008, Ismael .... wrote:

So is there no other way to do it but to verify the integrity using triggers
and drop the referential constraints?

Well, you could do something using a before delete trigger on the
referencing table that returns NULL to avoid the delete as well, but
making it only prevent the deletions caused by the referential constraints
might be difficult.

So is there no other way to do it but to verify the integrity using triggers
and drop the referential constraints?

Well, you could do something using a before delete trigger on the
referencing table that returns NULL to avoid the delete as well, but
making it only prevent the deletions caused by the referential constraints
might be difficult.

That's right, It's easier to verify the existence of the master before inserting
something in the details than controlling the way something gets deleted.
After all, is only a
PERFORM * FROM.... WHERE NEW.....
IF NOT FOUND THEN
RISE EXCEPTION 'that doesn't exists';...
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