Re: ORDER BY and NULLs

T E Schmitz <mailreg@numerixtechnology.de> writes:
> Greg Stark wrote:
>> Which book is it?

> PostgreSQL by Korry Douglas + Susan Douglas, ISBN 0-7357-1257-3; Feb 2003

Hmm, I've heard of that book but never seen it.  The authors are not
participants in the PG community --- AFAICT neither of them have ever
posted anything in the mailing lists.

> The paragraph continues:
> "If the SELECT command included the clause WHERE phone NOT NULL, 
> PostgreSQL could use the index to satisfy the ORDER BY clause.
> An index that covers optional (NOT NULL) columns will not be used to 
> speed table joins either."

My goodness, it seems to be a veritable fount of misinformation :-(

I wonder how much of this is stuff that is true for Oracle and they just
assumed it carried over?
        regards, tom lane