Re: arrays of foreign keys

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On 09/07/07 18:47, Max wrote:
> Hello,
>
> And pardon me if I posted this question to the wrong list, it seems
> this list is the most appropriate.
>
> I am trying to create a table with an array containing foreign keys.
> I've searched through the documentation and couldn't find a way to do
> so.
>
> Is this something that one can do?
>
> Basically, I have two tables:
>
> create table user (
>   user_id serial,
>   login varchar(50) primary key,
>   tags integer[]-- this is where the problem lies
> );
>
> create table tag (
>   tag_id serial,
>   name varchar(50) primary key
> );
>
> I would like the user.tags field to be a list of foreign keys (tag_ids
> specifically).
>
> I know I can solve my problem with the following table:
>
> create table user_tag (
>   user_id integer,
>   tag_id integer,
>   foreign key (user_id) references table user(user_id) on delete
> cascade,
>   foreign key (tag_id) references table tag(tag_id) on delete cascade,
>   primary key (user_id,tag_id)
> );
>
> But I would really like to avoid doing that.

Why?

The (literally) cardinal rule of database normalization is
"eliminate repeating values".

> Is there a solution to this problem with arrays of foreign keys, and
> if so, how does one do that?
>
> Thanks for any help.

- --
Ron Johnson, Jr.
Jefferson LA  USA

Give a man a fish, and he eats for a day.
Hit him with a fish, and he goes away for good!

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