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From: chidamparam muthusamy <[email protected]>
To: [email protected]
Cc: Pgsql Novice <[email protected]>
Subject: Re: How to use a cross column exclude constraint
Date: Tue, 23 Aug 2022 20:17:46 +0530
Message-ID: <CABUk_4iSF9MagtgSX9ox5ZOqX0hMLo+FVN=xcJHksSW=aUriHQ@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>

Refer https://www.postgresql.org/docs/current/ddl-constraints.html

CREATE TABLE products (
    product_no integer,
    name text,
    price numeric CHECK (price > 0),
    discounted_price numeric CHECK (discounted_price > 0),
    CHECK (price > discounted_price)
);

In the above example, column 'discounted_price'  value is checked that it
should be less than the column value, 'price'.
Is it possible to add similar check condition for the columns,
'record_a_id' and 'record_b_id' that is
CHECK(record_a_id != record_b_id)
Regards,
Chidamparam


On Mon, Aug 22, 2022 at 1:15 AM <[email protected]> wrote:

>
> Hi All,
>
> Schema:
>
> CREATE TABLE record (
>     id uuid primary key default ...,
>     ...
> );
>
> CREATE TABLE record_pointer (
>     id uuid primary key default ...,
>     record_a_id uuid not null references record (id),
>     record_b_id uuid not null references record (id),
>     ...
> );
>
>
> I am trying to create an exclude constraint to make both record_a_id and
> record_b_id unique table wide, so that each row from "record" can ever be
> referenced once in "record_pointers".
>
> Eg. if I add a record_pointer row that has "this-is-random-uuid" as
> record_a_id, the value "this-is-random-uuid" can never be in record_a_id or
> record_b_id in any other row.
>
>
> Thank you in advance!
>
>
>

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