Обсуждение: Time interval sums

How does one sum interval sums?

the following does not work:select sum(stop-start::interval) as total from startstop                      where sid
=545   and                            2006  = date_part('year', day)   and                            9 =
date_part('month',day)
 
however  select stop-start::interval) as total from startstop                      where sid    = 545   and
              2006  = date_part('year', day)   and                            9 = date_part('month', day)
 
works great but I need an overall sum
Table schema:         Table "public.startstop"Column |          Type          | Modifiers
--------+------------------------+-----------sid    | integer                | not nullstart  | time without time zone
|stop  | time without time zone |day    | date                   | not null
 

thanks


-- 
Arthur R. Van Hook     Mayor 
The City of Lake Lotawana

hook@lake-lotawana.mo.us

(816) 578-4704 - Home
(816) 578-4215 - City
(816) 564-0769 - Cell

"A. R. Van Hook" <hook@lake-lotawana.mo.us> writes:
> How does one sum interval sums?
> the following does not work:
>  select sum(stop-start::interval) as total from startstop

Define "does not work"?  What did you get, what were you hoping for?

Personally I'd drop the unnecessary cast, but AFAICS there are
appropriate operators at least as far back as 7.3.
        regards, tom lane