Re: CHECK Constraints

Thanks for the help. I just tried it, and it works.

For readers: this seems to work well as a substitute for the MySQL datatype 'enum'. We
are converting to PostgreSQL from MySQL. Looks like CHECK CONSTRAINT should
handle the MySQL enum feature quite nicely.

Just thought I would post the usage in case someone else is looking for a similar solution.

-----Original Message-----
From: Michael Fuhr [mailto:mike(at)fuhr(dot)org]
Sent: Fri 4/22/2005 12:19 PM
To: Van Ingen, Lane
Cc: pgsql-novice(at)postgresql(dot)org
Subject: Re: [NOVICE] CHECK Constraints

What happened when you tried it? A simple test should answer the
question.

CREATE TABLE foo (
id serial PRIMARY KEY,
price integer NOT NULL CHECK (price = 1 OR price = 2 OR price = 3)
);

INSERT INTO foo (price) VALUES (1);
INSERT 0 1

INSERT INTO foo (price) VALUES (2);
INSERT 0 1

INSERT INTO foo (price) VALUES (3);
INSERT 0 1

INSERT INTO foo (price) VALUES (0);
ERROR: new row for relation "foo" violates check constraint "foo_price_check"

INSERT INTO foo (price) VALUES (4);
ERROR: new row for relation "foo" violates check constraint "foo_price_check"

--
Michael Fuhr
http://www.fuhr.org/~mfuhr/ <http://www.fuhr.org/~mfuhr/>

-----Original Message-----
From: Bruno Wolff III [mailto:bruno(at)wolff(dot)to]
Sent: Fri 4/22/2005 12:37 PM
To: Van Ingen, Lane
Cc: pgsql-novice(at)postgresql(dot)org
Subject: Re: CHECK Constraints

On Fri, Apr 22, 2005 at 12:02:41 -0400,
"Van Ingen, Lane" <lvaningen(at)ESNCC(dot)com> wrote:
> Hi all,
> the 8.0 manual says CHECK can be used in the following manner:
> CHECK (expression)
> The only stipulations are that it must produce a boolean result (true or unknown) to succeed.
>
> If I were to specify a the following on a field named price in one expression, would it succeed?
> CHECK (price = 1 OR price = 2 OR price = 3)
>
> In other words, I would want to raise an exception on any other value other than 1, 2, or 3. Can
> this be done? All of the examples in the manual show a single check (like price > 0) .

Yes, you can do that.