Re: Time stamp diff function

We have NUMTODSINTERVAL, but not DSINTERVALTONUM, sadly. So a function like you make is probably needed, I think.

A couple small things I can think of:
1) There's a lot of repetition of code.
2) Why select from dual?

Point 1 makes not much difference performance wise. Point 2 makes unnecessary context switches between SQL and PL/SQL and can make a bit of performance difference.

My take on a rewrite would be:

create or replace function tsdiff(ts1 in timestamp, ts2 in timestamp, units in varchar2)
/* units - l=millisecond s=second, m=minute, h=hour, d=day */ return number
is
  diff interval day(9) to second(9) := ts1 - ts2; begin
  return (

             extract(day from diff)
           + extract(hour from diff)/24
           + extract(minute from diff)/24/60
           + extract(second from diff)/24/60/60
         ) * case (lower(units))
            when 'l' then 24*60*60*1000
            when 's' then 24*60*60
            when 'm' then 24*60
            when 'h' then 24
            when 'd' then 1
                     else null
         end;

There can be other rewrites that also would be fine, but this works on an 11.2 instance (at least with a few tests I made :-)

I am not quite sure - but perhaps the select from dual trick might be necessary on old versions, as PL/SQL didn't always have all SQL functions - maybe EXTRACT used to only SQL? I am not stating that for certain, but maybe...

Regards

Kim Berg Hansen

http://dspsd.blogspot.com
kibeha_at_gmail.com
_at_kibeha

On Fri, Nov 7, 2014 at 3:41 PM, Andrew Kerber <andrew.kerber_at_gmail.com> wrote:

> I don't typically work with time intervals a lot, so I am not really
> familiar with getting a difference between timestamps. I wrote the function
> below to subtract two timestamps. Does anyone have a better example of how
> to do this:
>
> create or replace function tsdiff(ts1 in timestamp, ts2 in timestamp,
> units in varchar2)
> /* units - l=millisecond s=second, m=minute, h=hour, d=day */
> return number
> is
> diffval number;
> unitsin char(1);
> begin
> unitsin:=lower(units);
> if unitsin='l'
> then
> select
> extract(day from (ts1-ts2))*24*60*60*1000
> + extract(hour from (ts1-ts2))*60*60*1000
> + extract(minute from (ts1-ts2))*60*1000
> + extract(second from (ts1-ts2))*1000
> into diffval
> from dual;
> elsif unitsin='s'
> then
> select
> extract(day from (ts1-ts2))*24*60*60
> + extract(hour from (ts1-ts2))*60*60
> + extract(minute from (ts1-ts2))*60
> + extract(second from (ts1-ts2))
> into diffval
> from dual;
> elsif unitsin='m'
> then
> select
> extract(day from (ts1-ts2))*24*60
> + extract(hour from (ts1-ts2))*60
> + extract(minute from (ts1-ts2))
> + extract(second from (ts1-ts2))/60
> into diffval
> from dual;
> elsif unitsin='h'
> then
> select
> extract(day from (ts1-ts2))*24
> + extract(hour from (ts1-ts2))
> + extract(minute from (ts1-ts2))/60
> + extract(second from (ts1-ts2))/60/60
> into diffval
> from dual;
> elsif unitsin='d'
> then
> select
> extract(day from (ts1-ts2))
> + extract(hour from (ts1-ts2))/24
> + extract(minute from (ts1-ts2))/24/60
> + extract(second from (ts1-ts2))/24/60/60
> into diffval
> from dual;
> end if;
> return diffval;
> end;
>
> Sent from my iPad--
> http://www.freelists.org/webpage/oracle-l
>
>
>

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