I have a view joining two tables with a (1 to 1) relationship. I am trying to
create two update
rules (1 rule for each table in the view). To accomplish this I am trying
(unsuccessfully) to use
the where condition syntax of the update rules.
Basically, I only want to update a table if the columns related to its tuple
are altered. If
possible, I don't want to update/touch a tuple from a table who's data remains
unchanged.
However, the where conditions that I am using to make this distinction are
giving the following
error:
"ERROR: cannot update a view"
"HINT: You need an unconditional ON UPDATE DO INSTEAD rule."
Ofcourse, if my understanding of the use of the rule's WHERE condition is why
off base, I would be
enteresting in knowing the proper way it should be used.
Here are my sample table, view, and rule definitions: <rule are at the bottom>
CREATE SEQUENCE public.person_seq
INCREMENT BY 1
START WITH 1
;
CREATE TABLE public.person
(
id integer primary key not null
default nextval('public.person_seq'),
name varchar(30) unique not null
)
;
ALTER SEQUENCE public.person_seq OWNED BY public.person.id;
CREATE TABLE public.husband
(
id integer primary key
references person(id),
tiesize integer not null
)
;
CREATE OR REPLACE VIEW public.vhusband (id, name, tiesize) AS
SELECT
A.id, A.name, B.tiesize
FROM
public.person as A
INNER JOIN
public.husband as B
ON
A.id = B.ID
;
CREATE OR REPLACE RULE
vhusband_update_person
AS ON UPDATE TO
public.vhusband
WHERE
-- this is where I am trying to constrain which table
-- gets updated. Since name in only in the person table.
(NEW.name)<>(OLD.name)
DO INSTEAD
(
UPDATE
public.person
SET
name = NEW.name
WHERE
id = OLD.id
)
;
CREATE OR REPLACE RULE
vhusband_update_husband
AS ON UPDATE TO
public.vhusband
WHERE
-- this is where I am trying to constrain which table
-- gets updated. Since tiesize in only in the husband table.
(NEW.tiesize)<>(OLD.tiesize)
DO INSTEAD
(
UPDATE
public.husband
SET
tiesize = NEW.tiesize
WHERE
id = OLD.id
)
;
Regards,
Richard Broersma Jr.
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