Re: Help with Arrays and References

On Mon, 24 Jun 2002, William N. Zanatta wrote:

> Hi,
>
>    I'm starting on PostgreSQL so please be patient; =]
>
>    I'm building a book library database in which I have a table
> TBL_FORMAT which keeps basic information on various file-formats (ie 1,
> PDF, Portable Document Format) and a TBL_BOOKS which I want to reference
> TBL_FORMAT. But the column Format inside TBL_BOOKS is an array, as a
> book may exist in one or more file types. My doubt is: If I make
> something like
>
>    CREATE TABLE "tbl_books" (
>    "id_book" int4 DEFAULT nextval('TBL_Books_ID_Books_Seq'::text) NOT NULL,
>    "format" _int4 NOT NULL REFERENCES TBL_Format ON_UPDATE CASCADE,
>    ...
>
>    will the CASCADE action update my TBL_Books (Format) keeping the
> other values in the array or will it erase all and set the new Format value?

That shouldn't even be legal assuming that tbl_format's key is an int.
The two types must be comparable which isn't true of int4 and _int4.
You're probably better off with a details table with the book's id and
format's id and appropriate references.