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List:       postgresql-sql
Subject:    [SQL] a tricky one
From:       Olaf Marc Zanger <olaf.zanger () soli-con ! com>
Date:       2001-02-24 15:55:40
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hi there, 

something brainboggling :-)

three tables:
fac with:
id                   | integer       | not null default 
nextval('fac_id_seq'::text)                                                   
 
pre with:
  id          | integer | not null default nextval('pre_id_seq'::text)
 fac_id      | integer |
 date        | date    |              
 production       | float8    |              

prd with:
 id                | integer | not null default nextval('prd_id_seq'::text)
 date              | date    |
 fac_id            | integer |
 prediction           | float8 |

the last two have constraints as foreign keys  "fac_id int4 references fac 
(id)"

pre has only one row per month
prd has one value per day

if i do a 

select

count(fac.id)
 as fac_id,
sum(prd.production)
 as prd_production,
sum(pre.prediction)
 as pre_prediction

from
fac,
pre,
prd

where
date_part('year',timestamp(prd.date))=date_part('year',timestamp(pre.date))
and
date_part('month',timestamp(prd.date))=date_part('month',timestamp(pre.date))
and
pre.fac_id=fac.id
and
prd.fac_id=fac.id

group by
fac.id

what i acctually want is a result that shows the summed production of a year 
and the summed prediction of a year at the same time 


i got values of 365 for fac_id before i had the constraints :-), which was 
perfectly well.

now it shows 
372 (like 31x12) if i keep it as is
4392 (like 365x12) if i ommit the month-where-clause.

what's wrong

can anybody help, this goes over my know-how :-)
happy weekend

and thanks for the great help lately from the list

olaf

-- 
soli-con Engineering Zanger, Dipl.-Ing. (FH) Olaf Marc Zanger
Lorrainestrasse 23, 3013 Bern / Switzerland
fon:+41-31-332 9782, mob:+41-76-572 9782
mailto:olaf.zanger@soli-con.com, http://www.soli-con.com

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