On Dec 16, 2009, at 10:41 AM, Jacek Kałucki wrote:
> So, compound keys as well aren't supported :(
> It's very bad news for me.
Yes, compound primary keys are supported. Modifying the values of
compound primary keys is not supported.
Primary keys are the only way of identifying a record. If you change
that value, you break the relationship between data in the application
and data in the database. You can get away with changing the PK in a
single-user system, since you're the only one who could possibly be
modifying a record, but you simply can't do this in any sort of multi-
user design.
That's why you should *never* use columns that have any meaning to a
user as your keys. If you need to enforce uniqueness of user-relevant
values (e.g., invoice number, customer name), then you can use things
such Unique indexes to guarantee that, but these should never be PKs.
-- Ed Leafe
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