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Thread: Inheritance

Inheritance

From
Hasnul Fadhly bin Hasan
Date:
Hi,

I'm just wondering, what real benefit does inheritance have?  When i
create two tables, one inherited from the other,
does that mean i have two tables with same duplicate data or actually
they are joined in the back end?


Thank you for any input regarding this matter.

Hasnul

Re: Inheritance

From
Tom Lane
Date:
Hasnul Fadhly bin Hasan <hasnulfadhly.h@mimos.my> writes:
> I'm just wondering, what real benefit does inheritance have?  When i
> create two tables, one inherited from the other,
> does that mean i have two tables with same duplicate data or actually
> they are joined in the back end?

It's more like an implicit UNION ALL.  There's no duplication, but when
you specify a SELECT/UPDATE/DELETE over the parent table, the child
table is implicitly processed as well.

            regards, tom lane

Re: Inheritance

From
"Tjibbe Rijpma"
Date:
When will the function inheritence be futher development? That Primary keys
work wil on both parent and child table.

Now a use one table and several table with the same foreign keys to that
table. And a function have to do two insert of update actions.

----- Original Message -----
From: "Tom Lane" <tgl@sss.pgh.pa.us>
To: "Hasnul Fadhly bin Hasan" <hasnulfadhly.h@mimos.my>
Cc: <pgsql-novice@postgresql.org>
Sent: Tuesday, December 21, 2004 4:45
Subject: Re: [NOVICE] Inheritance


> Hasnul Fadhly bin Hasan <hasnulfadhly.h@mimos.my> writes:
> > I'm just wondering, what real benefit does inheritance have?  When i
> > create two tables, one inherited from the other,
> > does that mean i have two tables with same duplicate data or actually
> > they are joined in the back end?
>
> It's more like an implicit UNION ALL.  There's no duplication, but when
> you specify a SELECT/UPDATE/DELETE over the parent table, the child
> table is implicitly processed as well.
>
> regards, tom lane
>
> ---------------------------(end of broadcast)---------------------------
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Re: Inheritance

From
Bruno Wolff III
Date:
On Tue, Dec 21, 2004 at 09:27:05 +0100,
  Tjibbe Rijpma <t.b.rijpma@student.tudelft.nl> wrote:
> When will the function inheritence be futher development? That Primary keys
> work wil on both parent and child table.

When someone does the work. This has been an open issue for a long time
and it doesn't seem to be a high priority for anyone.

> Now a use one table and several table with the same foreign keys to that
> table. And a function have to do two insert of update actions.

One reason that it probably isn't a high priority is you can do a lot of
the same stuff using views instead of inheritence.