Bill Anderson wrote: > Paul McNett wrote: >> Uwe Grauer wrote: >> >>> What is a table without a primary key good for? >>> Can you come up with a practical use for this? >>> >> An intermediary table for getting M:M joins that doesn't have any other >> meaningful information other than the two foreign keys really doesn't >> require a primary key. IOW: >> >> ... >> >> I've gotten in the habit of making a cust_cat.pk anyway, even though it >> isn't ever used anywhere. I could also do (cust_fk, cat_fk) as the PK >> but I've just never taken to that approach. > Technically you're correct, but what you have is really a compound > primary key. > > Where this comes into play is that the join table can have child tables, > which can have child tables themselves. All the keys would need to > propagate to the child/grandchild tables. Then what happens if you > change the customer PK value for some unknown reason? (Yes, it's not > supposed to happen...) An updating nightmare.
You never change a technical primary key value. > > You still want a PK on a join table. It's just easier maintenance all > around. Yes. _______________________________________________ Post Messages to: [email protected] Subscription Maintenance: http://leafe.com/mailman/listinfo/dabo-dev Searchable Archives: http://leafe.com/archives/search/dabo-dev This message: http://leafe.com/archives/byMID/dabo-dev/[EMAIL PROTECTED]
