Subject: simple problem???
From: ivan marchesini <marchesini@unipg.it>
Reply-To: marchesini@unipg.it
To: pgsql-sql@postgresql.org
Content-Type: text/plain
Organization: University of Perugia
Date: Thu, 20 Jul 2006 16:52:36 +0200
Message-Id: <1153407157.5192.64.camel@geoivan>
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Dear users....
It's a simple problem I think (and I hope  :-)

I have a table like this:
A|B|C
1|2|20
1|3|10
1|4|21
2|3|12
2|4|22
3|4|23

where the first two column are a combination without repetition (with
k=2) of the numbers 1,2,3,4
for each pair I have a value in the column C.

I would want a select that can extract these records:

1|3|10
2|3|12
3|4|23


i.e. the select must look into the A field first and: 
-select all records where A=1, 
-find, into this selection, the record where there's the minimum value
of the field C 
-print all the fields for this record.

then

-select all records where A=2
-find, into this selection, the record where there's the minimum value
of the field C 
-print all the fields of this record.

and so on...

using 
SELECT a,MIN(c) FROM table GROUP BY a

is a partial solution because I can't see the value of B
and I obtain:

1|10
2|12
3|23

How can I do for plotting also the value of B???

Thank you very much

Ivan


-- 
Ivan Marchesini
Department of Civil and Environmental Engineering
University of Perugia
Via G. Duranti 93/a 
06125
Perugia (Italy)
e-mail: marchesini@unipg.it
        ivan.marchesini@gmail.com
tel: +39(0)755853760
fax: +39(0)755853756
jabber: geoivan73@jabber.org