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From: Tom Lane <[email protected]>
To: David G. Johnston <[email protected]>
Cc: JORGE MALDONADO <[email protected]>
Cc: [email protected] <[email protected]>
Subject: Re: A situation with one parent table and 3 child tables
Date: Mon, 02 Oct 2023 23:03:04 -0400
Message-ID: <[email protected]> (raw)
In-Reply-To: <CAKFQuwZbmqeLoHBzuOkVjd4qXyNUi1tcuhf8bECK+2c-DGK9iw@mail.gmail.com>
References: <CAAY=A7_wHBKkKFxuxXc7A+fr3TYGmWS9-hCGghLRDcQAAa_wfQ@mail.gmail.com>
	<CAKFQuwZbmqeLoHBzuOkVjd4qXyNUi1tcuhf8bECK+2c-DGK9iw@mail.gmail.com>

"David G. Johnston" <[email protected]> writes:
> On Monday, October 2, 2023, JORGE MALDONADO <[email protected]> wrote:
>> I have one parent table (*table_p*) with 3 child tables (*table_ch1*, *table_ch2
>> *and *table_ch3*). Each record of the parent table can be associated with
>> 1 and only 1 child table records. This means that:
>> 
>> * Some records of the *table_p* will link to records of *table_ch1*
>> * Some records of the *table_p* will link to records of *table_ch2*
>> * Some records of the *table_p* will link to records of *table_ch3*
>> 
>> At first look, this does not make very much sense to me. I thought about
>> considering 3 parent tables, one for each child table. However, the 3
>> parent tables would have the same exact structure and I would like to know
>> if there is a workaround for this issue.

> You are thinking of it backwards.  Your chN tables will have FK pointing
> back to the p table.  I suggest adding some kind of type column to the p
> table indicating which chN table the row belongs to.

Do you need that?  I was wondering about converting the 3 child tables
into a partitioned table.  Then you can query them separately when
you need to, but you can also treat them as one table --- and you
can set up one FK constraint between that and the parent table.

			regards, tom lane

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