D. Dante Lorenso wrote:
I'd really like to have ORDER BY and LIMIT for UPDATE and DELETE
commands. Is this possible?
UPDATE invoice i
SET reserve_ts = NOW() + '1 hour'::timestamp
FROM account a
WHERE a.acct_id = i.acct_id
AND i.reserve_ts < NOW()
AND a.status = 'A'
AND i.is_paid IS FALSE
ORDER BY i.create_ts ASC
LIMIT 1
RETURNING invoice_id;
This query would find JUST ONE invoice record which is not paid and
reserve the right to operate on the row using the 'reserve_ts'
column for all active accounts. The one row would be the oldest
invoice matching the criteria. Only that one row would be updated
and the invoice_id of the updated row (if any) would be returned.
Can something like what I want be added in a future version? Ideas
or alternatives? I don't see how I can rewrite this query as a
single statement any other way and get the same expectations.
Doesn't this do it, assuming invoice_id is unique?
UPDATE invoice
SET reserve_ts = NOW() + '1 hour'::timestamp
where invoice_id =
(select invoice_id from invoice i,
account a
WHERE a.acct_id = i.acct_id
AND i.reserve_ts < NOW()
AND a.status = 'A'
AND i.is_paid IS FALSE
ORDER BY i.create_ts ASC
LIMIT 1)
RETURNING invoice_id;
- John Burger
MITRE
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