Subject RE: Keys :: was Re: [IBO] LookupCombo
Author Claudio Valderrama C.
> -----Original Message-----
> From: Helen Borrie [mailto:helebor@...]
> Sent: MiƩrcoles 2 de Mayo de 2001 3:21
> To further confuse, people coming from desktop dbs often think a
> key and an index are the same thing. They are not. It so
> happens that one of the things IB does to implement its rules for
> a primary key is to create a unique, non-nullable index for its
> column(s). Currently, it implements its rules for a foreign key
> by creating a non-unique, non-nullable index for it's column(s).

I either misunderstood the posting or there's a typo here. FKs are supported
by an underlying index that's non-unique, so it accepts NULL entries.
Otherwise, you couldn't create non-mandatory, non-identifying relationships
between entities (tables).

> This particular behaviour for foreign keys isn't always desirable
> - programmers want more control over indexes that are not on
> primary key columns - so Firebird is looking at making
> auto-creation of FK indexes optional.

Yuk, or at least be able to deactivate the FK's index (my current changes to
be tested privately.)