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From: "Dan Winslow" <d.winslow@cox.net>
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Subject: Diffcult query
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Date: Fri, 21 Mar 2003 17:41:29 GMT
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To: pgsql-sql@postgresql.org
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Hi folks. This is giving me fits. I feel like it oughta be simple, but
apparantly its not...I think.

Given a table :

create table tablea (
  code1 varchar(32),
  code2 varchar(32),
  cost    int
);

and the rows

code1    code2    cost
----------------------------------
"aaa"        "bbb"    2
"ddd"        "eee"    3
"bbb"        "aaa"    6
"ggg"         "hhh"    4

I need a ( preferably single ) query that will sum the costs for all unique
pairs of codes, without regard to column order. That is, for summing
purposes, rows 1 and 3 are identical, and should produce the sum of 8 for
the unordered pair("aaa","bbb"). It should also, of course, prevent the case
where ("bbb","aaa") is considered a seperate pair. Any ideas would be much
appreciated.