Re: ORDER BY and NULLs

Hello Tom,

Tom Lane wrote:
> 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 :-(


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