Обсуждение: insert into a view?

Tried it but didn't work.  It gave me a hint though to try triggers.
Can anyone show me how to do an insert into a view using triggers?
Thanks. :-)

On Mon, May 01, 2006 at 05:23:22PM -0700, Karen Hill wrote:
> Tried it but didn't work.  It gave me a hint though to try triggers.
> Can anyone show me how to do an insert into a view using triggers?

Rules are probably what you're after; the documentation has examples.

http://www.postgresql.org/docs/8.1/interactive/rules.html
http://www.postgresql.org/docs/8.1/interactive/rules-update.html#RULES-UPDATE-VIEWS

--
Michael Fuhr

"Karen Hill" <karen_hill22@yahoo.com> writes:
> Tried it but didn't work.  It gave me a hint though to try triggers.
> Can anyone show me how to do an insert into a view using triggers?

I hope it said rules, because you can't put a trigger on a view.

regression=# create table t(f1 int, f2 text);
CREATE TABLE
regression=# create view v as select * from t;
CREATE VIEW
regression=# insert into v values(22, 'foo');
ERROR:  cannot insert into a view
HINT:  You need an unconditional ON INSERT DO INSTEAD rule.
regression=# create rule r as on insert to v do instead
regression-# insert into t values(new.*);
CREATE RULE
regression=# insert into v values(22, 'foo');
INSERT 0 1
regression=# select * from t;
 f1 | f2
----+-----
 22 | foo
(1 row)


            regards, tom lane

Tom Lane wrote:

> I hope it said rules, because you can't put a trigger on a view.
>
> regression=# create table t(f1 int, f2 text);
> CREATE TABLE
> regression=# create view v as select * from t;
> CREATE VIEW
> regression=# insert into v values(22, 'foo');
> ERROR:  cannot insert into a view
> HINT:  You need an unconditional ON INSERT DO INSTEAD rule.
> regression=# create rule r as on insert to v do instead
> regression-# insert into t values(new.*);
> CREATE RULE
> regression=# insert into v values(22, 'foo');
> INSERT 0 1
> regression=# select * from t;
>  f1 | f2
> ----+-----
>  22 | foo
> (1 row)

Thanks Tom,

I tried it and it worked.  Is it possible to do something a bit more
complex?  Can you use rules to insert into a view that has multiple
tables as the source?  For example:

CREATE VIEW v AS SELECT * FROM t1, t2 WHERE t1.num = t2.num;

Would the rule for the above look something like this?

CREATE RULE r AS ON INSERT INTO t1, t2 WHERE t1.num = t2.num DO INSTEAD
INSERT INTO t1 , t2 VALUES (new.*);

On Wed, May 03, 2006 at 10:02:17AM -0700, Karen Hill wrote:
>
> Tom Lane wrote:
>
> Thanks Tom,
>
> I tried it and it worked.  Is it possible to do something a bit more
> complex?  Can you use rules to insert into a view that has multiple
> tables as the source?  For example:
>
> CREATE VIEW v AS SELECT * FROM t1, t2 WHERE t1.num = t2.num;

Not related directly to your issue, but you may find that explicit
JOINs help are easier to debug and maintain, as in:

CREATE VIEW v AS
SELECT t1.*, t2.foo, t2.bar
FROM
    t1
JOIN
    t2
    ON (t1.num = t2.num);

> Would the rule for the above look something like this?
>
> CREATE RULE r AS ON INSERT INTO t1, t2 WHERE t1.num = t2.num DO INSTEAD
> INSERT INTO t1 , t2 VALUES (new.*);

More like this:

CREATE RULE r AS
    ON INSERT INTO v
    DO INSTEAD (
        INSERT INTO t1 VALUES (NEW.num, NEW.baz, NEW.blur, NEW.quux);
        INSERT INTO t2 VALUES (NEW.num, NEW.foo, NEW.bar);
    );

HTH :)

Cheers,
D
--
David Fetter <david@fetter.org> http://fetter.org/
phone: +1 415 235 3778        AIM: dfetter666
                              Skype: davidfetter

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