Re: Array of foreign key

On Sun, Dec 24, 2017 at 1:11 AM, Daevor The Devoted <dollien(at)gmail(dot)com>
wrote:

>
> Le 23 déc. 2017 20:25, "Peter J. Holzer" <hjp-pgsql(at)hjp(dot)at> a écrit :
>
> I think the OP wants something like this:
>
> create table features (
> id serial primary key,
> name varchar not null
> );
>
> create table products (
> id serial primary key,
> name varchar not null,
> array_of_features int[]
> references [] features(id) -- XXX - invented syntax
> );
>
> where products.array_of_features can only contain integers from
> features.id. This doesn't currently (as of 10.1) work.
> As I wrote, you could use triggers, but there is no way to declare that
> foreign key directly.
>
>
> This is an interesting feature you are talking about. However, I'm not
> sure I properly understand the use-case(s). Could you perhaps please give
> some examples to help me understand? (I don't just mean some SQL code, I
> mean an explanation of the business use-cases served by the code).
>

Other than Peter's simple example above, you could implement a simple RBAC
system this way. As with the features example above, you would have a
table of roles that are referenced by a user table. In this case, you
would need an int array with foreign key constraints on each element in
the array to the id column in the role table.