Re: Advice about a parent-child relation design - Mailing list pgsql-novice

From Gavin Flower
Subject Re: Advice about a parent-child relation design
Date
Msg-id 5650D3C0.3090702@archidevsys.co.nz
Whole thread Raw
In response to Advice about a parent-child relation design  (JORGE MALDONADO <jorgemal1960@gmail.com>)
List pgsql-novice
On 22/11/15 06:45, JORGE MALDONADO wrote:
> I have 2 tables: parent and child. One of the fields, which should
> supposedly be part of the parent table, might occassionaly be
> different for one of the child table records.
>
> ParentTable
> * id
> * date
> * customer  <-----
> * reference
> * other fields...
>
>
> ChildTable
> * id-parent
> * document type
> * customer  <-----
>
> It is possible that the customer field is not the same for all of the
> child records. This is a very specific (and strange) situation that
> might eventually appear in the information system I am developing. I
> suppose that such a field must be part of the child table even if this
> case does not appear frequently.
>
> I am writing to ask for your feedback and see if there is another
> possible approach.
>
> With respect,
> Jorge Maldonado

This might be useful (see my other post)

SELECT
     COALESCE(c.alternate_customer, p.customer)
FROM
     child c,
     parent p
WHERE
     p.id = c.id;


Cheers,
Gavin


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