Re: UPDATE of several columns using SELECT statement

On Tue, Mar 17, 2009 at 05:57:01PM +0100, adam.slachta wrote:
> Do you think there might be a way how to solve this not leading into
> splitting the update into two separate update statements for each of the two
> columns (max_breach, limit_value) ?

That's quite a query; I'm guessing it's from Oracle as it refers to a
NVL function and that this should be translated into COALESCE for PG.
Would the following do what you want:

UPDATE limit_breach lb SET
limit_value = ov.hedge_limit,
max_breach = ov.max_breach
FROM (
SELECT hedging_desk, idmarket, symbol, limit_name, hedge_limit,
ABS(ov.outright_volume) - COALESCE(ov.hedge_limit,0) AS max_breach
FROM outrightvolume_breach) ov
WHERE lb.hedging_desk = ov.hedging_desk
AND lb.idmarket = ov.idmarket
AND lb.symbol = ov.symbol
AND lb.limit_name = ov.limit_name
AND lb.breach_end IS NULL
AND lb.max_breach <= ov.max_breach;

I've obviously not tested it, but I think it's correct. It's also got
the advantage of much less duplication of code.

--
Sam http://samason.me.uk/