UNION and rows improperly unified: query optimization question

Greetings. I have an accounting system in Postgres which has tables
'transact' and 'gl_entry'. Each check, deposit, etc has one entry in
transact, but there may be multiple entries in gl_entry if one check was for
multiple expenses that are tracked separately (for example, one check to AT&T
might cover both telephone and Internet service, which are two different
costing categories). Also, debit and credit are supposed to appear in
seperate columns, even though they are one number with either positive or
negative sign in the table. So I run two select and combine them
using a union statement, but this improperly combines two gl_entry lines that
do not differ in amount or transaction ID. My solution is to select also the
unique ide number from gl_entry and remove it by wrapping the
SELECT...UNION...SELECT in another SELECT. This seems awfully ugly. Is there
a better way?

Here is the query that I use now, which produces correct results:

SELECT postdate, person, debit, credit, descr, num FROM (    SELECT t.postdate, t.person, abs(g.amt) AS debit, '0.00'
AScredit, t.descr, t.num, g.id AS gid    FROM transact t, gl_entry g ' +    WHERE t.id = g.transact_id AND g.amt >=
0UNION   SELECT t.postdate, t.person, '0.00' AS debit, abs(g.amt) AS credit, t.descr, t.num, g.id AS gid    FROM
transactt, gl_entry g    WHERE t.id = g.transact_id AND g.amt < 0 
) AS subselect ORDER BY postdate

I would like to get rid of the outer SELECT, if possible.

--
Henry House
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