On Thursday 08 May 2003 7:40 am, David Loh wrote:
> Hi all.
> After some read of postgres' documentations, I can't found any command
> perform similar task like timediff() in other SQL server, the only thing I
> got is date_part(). For my case, what I actually need is to create a
> trigger (before insert) that check previous record (1 mins), grab the
> previous value and deduct new value (NEW.myValue := Previous.myValue -
> NEW.myOtherValue), and since the records are insert every minutes,the
> function should trace back to the record entered a minute ago (for e.g,
> 12:38 will check for record of 12:37 and grab the value), hence timestamp
> even include the milli-second, is there any command/trick to check if the
> record are entered approximately 55-65 secs (1 minutes +/- 5 secs) ?
Do exactly as you've just described:
SELECT ....
WHERE t BETWEEN now()-'1 min 5 secs'::interval AND now()-'55 secs'::interval
It takes a while to get used to PG's date/time/interval types vs timediff()
functions you get in most systems. I find them clearer now I've got used to
them.
-- Richard Huxton
