Re: SQL Rule

[Alban Hertroys <alban(at)magproductions(dot)nl>]

Bert wrote:
> Hi list
>
> I have a table construction like the one seen below, when i am updating
> or inserting i get a recurion, logical. But how to manage it that the
> rule is just doing it one time. Or is it possible to do the sum of a
> and b in an other way?
>
> CREATE TABLE test
> (
>   a int2,
>   b int2,
>   c int2,
>   id int2 NOT NULL,
>   CONSTRAINT id_test PRIMARY KEY (id)
> )
> WITHOUT OIDS;

You do know you can write this like this?:
CREATE TABLE test
(
  a int2,
  b int2,
  c int2,
  id int2 NOT NULL PRIMARY KEY
)
WITHOUT OIDS;

> CREATE OR REPLACE RULE sum_op AS
>     ON INSERT TO test DO  UPDATE test SET c = new.a + new.b
>   WHERE test.id = new.id;

How do you expect to update a record that doesn't exist yet?

I suppose what you meant is something like this (didn't check the 
syntax, but the INSTEAD part is important):

CREATE OR REPLACE RULE sum_op AS
    ON INSERT TO TEST DO INSTEAD
    INSERT (a, b, c, id) VALUES (new.a, new.b, new.a + new.b, new.id);

But as others suggested, a view is probably the better way to go.

Regards,
--
Alban Hertroys
alban(at)magproductions(dot)nl

magproductions b.v.

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