Re: combine SQL SELECT statements into one

[Chris.Ellis@xxxxxxxxxxxxxxxxx]

> > -----Original Message-----
> > From: Chris.Ellis@xxxxxxxxxxxxxxxxx 
> > [mailto:Chris.Ellis@xxxxxxxxxxxxxxxxx] 
> > Sent: Monday, February 01, 2010 4:08 AM
> > To: neilstylz@xxxxxxxxx
> > Cc: pgsql-general@xxxxxxxxxxxxxx
> > Subject: Re: combine SQL SELECT statements into one
> > 
> > 
> > Hi 
> > 
> > pgsql-general-owner@xxxxxxxxxxxxxx wrote on 02/01/2010 07:36:55
AM:
> > 
> > > Good Evening, Good Morning Wherever you are whenever you
> > may be reading this. 
> > > 
> > > 
> >         snip 
> > >   
> > > count1 |  count2  | count3
> > > -------------------------------
> > >  2              2
             4 
> > > 
> > > Can this be done with ONE SQL STATEMENT? touching the 
> > database only ONE time? 
> > 
> > You can do the following: 
> > 
> > SELECT 
> >         (SELECT COUNT(distinct model) FROM
inventory WHERE 
> > modified >= '2010-02-01') AS "COUNT_1",
> >        (SELECT COUNT(distinct model) FROM
inventory WHERE 
> > modified >= '2010-01-20') AS "COUNT_2",
> >        (SELECT COUNT(distinct model) FROM
inventory WHERE 
> > modified >= '2010-01-01') AS "COUNT_3" 
> > ; 
> > 
> > PostgreSQL allows sub-queries in the select list as long as 
> > the sub-query returns one column 
> > 
> > Job done 
> > 
> > > Please let me know. 
> > >   
> > > Thanx> :)
> > > NEiL
> > >   
> > 
> > Chris Ellis 
> > 
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> 
> Original poster asked for the sql that will touch inventory table
only
> once.
> 
> Your statement (with 3 subqueries) will do it 3 times.
> Igor Neyman
> 

---
I think you will find that the poster asked to touch
the DATABASE not the TABLE only once:

        'Can this be done
with ONE SQL STATEMENT? touching the database only ONE time?'

While the sugested query might not me as optimised
as possible, it demonstrates a possible method of folding multiple select
statements into one select statement.  This seemed 
main purpose of this post.  I made the assumption
that the intent was to reduce the overhead and latency caused from sending
multiple statements.
 
Chris Ellis