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Re: CHILD WITHOUT PARENT (TEMPORARILY)

From: Jasen Betts <jasen(at)xnet(dot)co(dot)nz>
To: pgsql-novice(at)postgresql(dot)org
Subject: Re: CHILD WITHOUT PARENT (TEMPORARILY)
Date: 2009-12-29 02:40:03
Message-ID: hhbq63$dgs$1@reversiblemaps.ath.cx (view raw or flat)
Thread:
Lists: pgsql-novice
On 2009-12-28, JORGE MALDONADO <jorgemal1960(at)gmail(dot)com> wrote:

> I am developing an app in which there are 2 tables: a parent and a child.
> The difference is that, in my case, the child table is generated first and,
> if the user decides to keep the information then a record is generated in
> the parent table and the child table is connected to its parent. The field
> in the child table that connects to its parent is temporarily filled with a
> value of -1. The user who types the information may decide to keep or not
> the records in the child table and it is at this time when a record in the
> parent table is generated or not. Meanwhile, the records in the child table
> have a tamporary value of -1 in the field that will connect to its parent
> table and this causes me not to be able to define a foreign key.
> Please advice.

One fix is to use NULL instead of -1

Another is to make the connstraint DEFERRABLE INITIALLY DEFERRED and 
create the child records inside a transaction not COMMITing the 
tranaction until thwey have been UPDATEd with the correct foreign key
value,

A third is to create a record in the parent table with a key of -1


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