Re: ORDER BY and NULLs

Hello Tom,

Tom Lane wrote:
> T E Schmitz <mailreg(at)numerixtechnology(dot)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 :-(

Well, that's great. My knowledge of SQL is good enough to model a DB and
do run of the mill queries; but when it comes to some fine details I
rely on sensible input ;-)

Thanks for chipping in here and answering what I thought was a dummy
question.

--

Kind Regards/Gruß,

Tarlika