Thread: [GENERAL] Constraint + where

Hi guys,

I've got a column 'type_note' on a new table that it's being designed:

type_note varchar(32) NOT NULL;

On that column, there will be three different data:

1. yes

2. no

3. maybe

I wanna create a FK but just when the data on that column is = maybe.

How can I do that? Thanks!

On Sun, Mar 19, 2017 at 8:16 PM, Patrick B <patrickbakerbr@gmail.com> wrote:

Hi guys,

I've got a column 'type_note' on a new table that it's being designed:

type_note varchar(32) NOT NULL;

On that column, there will be three different data:

1. yes

2. no

3. maybe

I wanna create a FK but just when the data on that column is = maybe.

How can I do that? Thanks!

Why just "maybe"? Since there can only be three valid answers, why not FK for all three?

--

On Sun, Mar 19, 2017 at 8:16 PM, Patrick B <patrickbakerbr@gmail.com> wrote:

Hi guys,

I've got a column 'type_note' on a new table that it's being designed:

type_note varchar(32) NOT NULL;

On that column, there will be three different data:

1. yes

2. no

3. maybe

I wanna create a FK but just when the data on that column is = maybe.

How can I do that? Thanks!

Why just "maybe"? Since there can only be three valid answers, why not FK for all three?

--

Melvin Davidson
I reserve the right to fantasize.  Whether or not you
wish to share my fantasy is entirely up to you.

2017-03-20 13:27 GMT+13:00 Melvin Davidson <melvin6925@gmail.com>:

On Sun, Mar 19, 2017 at 8:16 PM, Patrick B <patrickbakerbr@gmail.com> wrote:

Hi guys,

I've got a column 'type_note' on a new table that it's being designed:

type_note varchar(32) NOT NULL;

On that column, there will be three different data:

1. yes

2. no

3. maybe

I wanna create a FK but just when the data on that column is = maybe.

How can I do that? Thanks!

Why just "maybe"? Since there can only be three valid answers, why not FK for all three?

--

I was able to get what I needed this way:

create table testing_fk_conditional_1 (
id serial NOT NULL PRIMARY KEY,
account_id bigint,
user_id bigint,
type_note integer NOT NULL,
CHECK (type_note = 100 AND user_id IS NOT NULL OR type_note = 200 AND account_id IS NOT NULL)
);