Обсуждение: optimize/cleanup SQL

For some reason this doesn't give me satisfaction that it's written
optimally, but I haven't found another way.

  SELECT round(CAST ((EXTRACT(EPOCH FROM clockout)
              -EXTRACT(EPOCH FROM clockin))/3600 AS NUMERIC),2) AS hours
    FROM timeclock;

The clockin and clockout columns are of type timestamp.

Is there a faster way to achieve this?  If not faster, a cleaner way
that executes as fast?


--
Brandon

On Fri, 29 May 2009 08:13:32 -0500 (CDT)
Brandon Metcalf <brandon@geronimoalloys.com> wrote:

> For some reason this doesn't give me satisfaction that it's written
> optimally, but I haven't found another way.
>
>   SELECT round(CAST ((EXTRACT(EPOCH FROM clockout)
>               -EXTRACT(EPOCH FROM clockin))/3600 AS NUMERIC),2) AS
> hours FROM timeclock;

satisfying?

template1=# select extract(days from ('2009-01-01'::timestamp -
'2008-01-01'::timestamp))+5::int;

?column?
----------
      371
(1 row)


--
Ivan Sergio Borgonovo
http://www.webthatworks.it

Brandon Metcalf <brandon@geronimoalloys.com> writes:
> For some reason this doesn't give me satisfaction that it's written
> optimally, but I haven't found another way.

>   SELECT round(CAST ((EXTRACT(EPOCH FROM clockout)
>               -EXTRACT(EPOCH FROM clockin))/3600 AS NUMERIC),2) AS hours
>     FROM timeclock;

> The clockin and clockout columns are of type timestamp.

timestamp, or timestamptz?  extract(epoch from timestamptz) is really
quite a cheap operation; there's no need to worry about performance
in that case.  If what's bothering you is ugliness, encapsulate this
as an inlineable SQL function.

            regards, tom lane