Re: Advice about a parent-child relation design

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