Re: [GENERAL] Constraint + where - Mailing list pgsql-general

From Patrick B
Subject Re: [GENERAL] Constraint + where
Date
Msg-id CAJNY3iu1u=BRr5xpQCFtew-XzH-Tq6Vf3Ckq9i7+5iSyinuhdQ@mail.gmail.com
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In response to Re: [GENERAL] Constraint + where  (Melvin Davidson <melvin6925@gmail.com>)
Responses Re: [GENERAL] Constraint + where  (Melvin Davidson <melvin6925@gmail.com>)
List pgsql-general


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)
);

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