Subject Re: [firebird-support] Re: index and foreigner key
thanks for your help adam

> You have 2 indices because WinDesign specifically declared an index as
> well as declaring the a foreign key constraint which implicitly
> creates an index.
> The reason is pretty simple, it speeds up the check to make sure the
> foreign key constraint is not being violated (in most cases, I wish
> there was a flag to disable it on certain low selectivity indices, but
> that is for another day).
> Do not create an ascending index on any set of fields that is defined
> as the primary key, any set of fields that is constrained as unique,
> or any field that is a foreign key.
> 1. It is unnecessary, it takes up space in your database, uses up
> additional resources during inserts, updates and deletes, and provides
> no benefit to selects, updates or deletes.
> 2. In the worst case, the optimiser may be confused and choose to use
> neither.
> Another thing, do not reply to another post. Yahoo Groups is threaded,
> which means that people using Newsreaders can choose to ignore an
> entire thread if it is not of interest for them. These people will
> never see your question. Changing the subject is not sufficient, the
> flag is inside the header of the email. Instead, compose a new email
> and everyone will see it.
> Adam
> _