From: | Louis-David Mitterrand <vindex+lists-pgsql-sql(at)apartia(dot)org> |
---|---|
To: | pgsql-sql(at)postgresql(dot)org |
Subject: | Re: check constraint on multiple tables? |
Date: | 2010-03-03 16:17:59 |
Message-ID: | 20100303161759.GB22889@apartia.fr |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-sql |
On Wed, Mar 03, 2010 at 04:05:43PM -0000, Oliveiros wrote:
>
> As your table names seem to imply, type and category are cabin's
> characteristics , not ship characteristics.
> Am I right?
Yes and no :)
- I'm scanning cruise line web sites with a spider to collect prices so
I'm building cabin_type's and cabin_category's on the fly,
- each ship class (a cruise line has several) has its own particular
types (Celebrity Xpedition is the only one with "Xpedition suite"
type, etc.)
> As Richard pointed out, maybe you could add a relationship between
> cabin and ship and drop the relationship between ship and
> cabin_category you now have
> Then you could add that uniqueness restriction.
That's one option.
> Also, the relationship between type and category is one to many ? Or
> can it be many to many? Put other way, is this overlap between the
> categories that belong to different "types" ?
One cabin_type to many cabin_category's, for example:
- "Sunset Veranda Stateroom" (type) can be on "Vista", "Panorama", etc.
decks (category) with a different price,
But it's true that there is some overlap in categories between different
ships.
> If the later applies, maybe
> you could have cabin refer to both type and category tables and drop
> the relation between type and category.
>
> The cabin table would then work as an associative table between
> category and type.
>
> Ain't saying your schema is wrong, maybe you have strong reasons to
> do that that way, that I am not realizin by now...
You got me thinking about it. Thank you for your interesting comments.
From | Date | Subject | |
---|---|---|---|
Next Message | Louis-David Mitterrand | 2010-03-03 16:21:19 | Re: check constraint on multiple tables? |
Previous Message | Little, Douglas | 2010-03-03 16:13:48 | Re: check constraint on multiple tables? |