First/Last in a group by

Question

Hi !
I have a table with session_ids, url a user visited and the time the did it.
I need output pr. session_id
Session id, durtaion of the session, the first page he visted, the last page he visited
I have tried a lot with first_value, last_value, first/last in various analytic functions, but my head cant seem to find the correct solution.
(aprt from coding it in PL/SQL)
This is an example of my table:
drop table mette_interval;
create table mette_interval (session_i number, url varchar2(400), url_time date);
insert into mette_interval values (1, 'start page', sysdate);
insert into mette_interval values (1, 'xxxxside z', sysdate+interval '5' second);
insert into mette_interval values (1, 'end pagexxxxxside z', sysdate+interval '6' second);
insert into mette_interval values (2, 'page xxx z',sysdate+interval '0' second);
insert into mette_interval values (2, 'page yyyy z', sysdate+interval '10' second);
insert into mette_interval values (3, 'page whatever z', sysdate+interval '1' second);
select session_i, (max(url_time)-min(url_time))*24*60*60 duration
from mette_interval
group by session_i;
Can you give me a hint?
Regards
Mette

Answer 1

SQL> select * from mette_interval;
SESSION_I URL                  URL_TIME
         1 start page           24-MAR-09
         1 xxxxside z           24-MAR-09
         1 end pagexxxxxside z  24-MAR-09
         2 page xxx z           24-MAR-09
         2 page yyyy z          24-MAR-09
         3 page whatever z      24-MAR-09
6 rows selected.
SQL> select session_i,(max(url_time)-min(url_time))*24*60*60 duration,
  2        max(url) keep(dense_rank first order by url_time) frst,
  3        max(url) keep(dense_rank last order by url_time) lst
  4   from mette_interval
  5   group by session_i;
SESSION_I   DURATION FRST                 LST
         1          6 start page           end pagexxxxxside z
         2         10 page xxx z           page yyyy z
         3          0 page whatever z      page whatever zToo Late...
Edited by: jeneesh on Mar 24, 2009 12:38 PM