Re: Can a field be a primary key as well as a foreign key?

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От Jan Wieck
Тема Re: Can a field be a primary key as well as a foreign key?
Дата
Msg-id 200203122145.g2CLjTU31327@saturn.janwieck.net
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Ответ на Can a field be a primary key as well as a foreign key?  (Andrew Snow <andrew@modulus.org>)
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Andrew Snow wrote:
>
>
> Can anyone see any problem with the following, practice?

    No  problem  at  all.  With  that  setup there can never be a
    subchild without the  matching  child,  even  if  the  parent
    exists.  If  a  child is deleted, it's subchildren follow, no
    need to touch the parent.  If that's the relationship of  the
    data, go ahead.


Jan

>
>
> CREATE TABLE parent (
>   foo SERIAL PRIMARY KEY
> );
>
> CREATE TABLE child (
>   foo INTEGER PRIMARY KEY REFERENCES parent ON DELETE CASCADE,
>   bar TEXT
> );
>
> CREATE TABLE subchild (
>   foo INTEGER PRIMARY KEY REFERENCES child ON DELETE CASCADE,
>   bar2 TEXT
> );
>
>
> ---------------------------(end of broadcast)---------------------------
> TIP 4: Don't 'kill -9' the postmaster
>


--

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