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 still want a PK on a join table. It's just easier maintenance all around. Bill _______________________________________________ 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]
