Re: Is it possible to redirect an update/insert/delete to a different table?

Hi Andreas,

The rule you've given only works for an update which changes the name.

If I do another update which changed the colour instead of the name, that
rule wouldn't do the right thing.

Instead, I'm looking for something which, with a single 'rule' (or whatever
the mechanism ends up being), intercepts *any* update on apples, and applies
the changes to the pears table instead, as if the only change that occurred
was a change of table name.

I can achieve this in the application which generates the sql commands, but
someone else suggested it was possible with rules, but it may not be the
case.

Thanks!
Andy




-----Original Message-----
From: pgsql-sql-owner@postgresql.org [mailto:pgsql-sql-owner@postgresql.org]
On Behalf Of Andreas Kretschmer
Sent: 20 November 2005 16:17
To: pgsql-sql@postgresql.org
Subject: Re: [SQL] Is it possible to redirect an update/insert/delete to a
different table?

Andy Ballingall <andy@areyoulocal.co.uk> schrieb:

> Hello Peter,
>
> I'm glad it's possible, but I can't see how from the documentation.
>
> Say if I have a table called 'apples' and a table called 'pears'.
>
> What would the rule look like that would remap all updates on apples so
that
> they were applied to pears instead?

create rule apples_pears_update as on update to apples do instead update
pears set name= NEW.name where id=NEW.id ;

test=# select * from apples ;id | name
----+------ 1 | a
(1 row)

test=# select * from pears ;id | name
----+------ 1 | b
(1 row)

test=# update apples set name = 'c' where id = 1;
UPDATE 1
test=# select * from pears ;id | name
----+------ 1 | c
(1 row)


http://www.postgresql.org/docs/8.1/interactive/rules-update.html

HTH, Andreas
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