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From: Josh Berkus <josh@agliodbs.com>
Reply-To: josh@agliodbs.com
Organization: Aglio Database Solutions
To: greg@turnstep.com, pgsql-sql@postgresql.org
Subject: Re: conversi ms-sql7 vs postgresql 7.3
Date: Mon, 10 Feb 2003 13:40:54 -0800
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Greg,

> > command in ms-sql 7 can use calculate field (column) balance from id=3D1
> > to id=3D4: "update xx set bal=3Dbalance=3Dbal+debet-credit"
>=20
> You cannot do such a thing in SQL alone: you must use a procedural=20
> language. One way is with plpgsql:

You're mistaken, I think (I can't find the original e-mail in this thread)

UPDATE totals SET balance =3D total_bal
FROM (SELECT acct_id, (sum(credit) - sum(debit)) as total_bal
	FROM accounts GROUP BY acct_id) tb
WHERE tb.acct_id =3D totals.acct_id
	AND totals.acct_id =3D $selection

... would update a ficticious "totals" table with the sum of credits and=20
debits for a particular account.
--=20
-Josh Berkus
 Aglio Database Solutions
 San Francisco