SQL Query to return multiple transactions in a 5 min. period

Question

I have been asked to write a query that scans a table of financial transactions looking for more than 1 transaction by the same person (EmplID for example) within a 5 minute period. I am not sure if this is possible with SQL. Here are the details:
Table = MEALTRANSLEDGER
Relevant Columns:
"TRANDATE" DATE,
"EMPLID" NUMBER(9,0)
I need to select these columns when a particular EmplID has logged more than 1 transaction in a 5 minute period.
I know I could do this with PL/SQL or Perl by stepping through the rows of the table and calculating date differences, but I would really like to know if SQL could do it.
Thanks for the help.
Version Info:
SQL> select * from v$version where banner like 'Oracle%';
BANNER
Oracle Database 10g Release 10.2.0.4.0 - Production

Answer 1

You can use something along these lines to determine the minutes difference between transactions...
SQL> ed
Wrote file afiedt.buf
  1  with t as (select 1 as emplid, to_date('01/01/2010 09:00:00', 'DD/MM/YYYY HH24:MI:SS') as trandate from dual union all
  2             select 1, to_date('01/01/2010 09:10:00', 'DD/MM/YYYY HH24:MI:SS') from dual union all
  3             select 1, to_date('01/01/2010 09:20:00', 'DD/MM/YYYY HH24:MI:SS') from dual union all
  4             select 1, to_date('01/01/2010 09:45:00', 'DD/MM/YYYY HH24:MI:SS') from dual union all
  5             select 1, to_date('01/01/2010 09:51:00', 'DD/MM/YYYY HH24:MI:SS') from dual union all
  6             select 2, to_date('01/01/2010 09:12:00', 'DD/MM/YYYY HH24:MI:SS') from dual union all
  7             select 2, to_date('01/01/2010 09:18:00', 'DD/MM/YYYY HH24:MI:SS') from dual union all
  8             select 2, to_date('01/01/2010 09:22:00', 'DD/MM/YYYY HH24:MI:SS') from dual union all
  9             select 2, to_date('01/01/2010 09:30:00', 'DD/MM/YYYY HH24:MI:SS') from dual union all
10             select 3, to_date('01/01/2010 09:05:00', 'DD/MM/YYYY HH24:MI:SS') from dual union all
11             select 3, to_date('01/01/2010 10:10:00', 'DD/MM/YYYY HH24:MI:SS') from dual union all
12             select 3, to_date('01/01/2010 11:15:00', 'DD/MM/YYYY HH24:MI:SS') from dual
13            )
14  --
15  select emplid, trandate
16        ,(trandate-lag(trandate) over (partition by emplid order by trandate)) * (24*60) as mins_diff
17  from t
18* order by emplid, trandate
SQL> /
    EMPLID TRANDATE             MINS_DIFF
         1 01/01/2010 09:00:00
         1 01/01/2010 09:10:00         10
         1 01/01/2010 09:20:00         10
         1 01/01/2010 09:45:00         25
         1 01/01/2010 09:51:00          6
         2 01/01/2010 09:12:00
         2 01/01/2010 09:18:00          6
         2 01/01/2010 09:22:00          4
         2 01/01/2010 09:30:00          8
         3 01/01/2010 09:05:00
         3 01/01/2010 10:10:00         65
         3 01/01/2010 11:15:00         65
12 rows selected.And then you can wrap that up to just highlight the problem ones...
SQL> ed
Wrote file afiedt.buf
  1  with t as (select 1 as emplid, to_date('01/01/2010 09:00:00', 'DD/MM/YYYY HH24:MI:SS') as trandate from dual union all
  2             select 1, to_date('01/01/2010 09:10:00', 'DD/MM/YYYY HH24:MI:SS') from dual union all
  3             select 1, to_date('01/01/2010 09:20:00', 'DD/MM/YYYY HH24:MI:SS') from dual union all
  4             select 1, to_date('01/01/2010 09:45:00', 'DD/MM/YYYY HH24:MI:SS') from dual union all
  5             select 1, to_date('01/01/2010 09:51:00', 'DD/MM/YYYY HH24:MI:SS') from dual union all
  6             select 2, to_date('01/01/2010 09:12:00', 'DD/MM/YYYY HH24:MI:SS') from dual union all
  7             select 2, to_date('01/01/2010 09:18:00', 'DD/MM/YYYY HH24:MI:SS') from dual union all
  8             select 2, to_date('01/01/2010 09:22:00', 'DD/MM/YYYY HH24:MI:SS') from dual union all
  9             select 2, to_date('01/01/2010 09:30:00', 'DD/MM/YYYY HH24:MI:SS') from dual union all
10             select 3, to_date('01/01/2010 09:05:00', 'DD/MM/YYYY HH24:MI:SS') from dual union all
11             select 3, to_date('01/01/2010 10:10:00', 'DD/MM/YYYY HH24:MI:SS') from dual union all
12             select 3, to_date('01/01/2010 11:15:00', 'DD/MM/YYYY HH24:MI:SS') from dual
13            )
14  --
15  select emplid, trandate
16  from (
17        select emplid, trandate
18              ,(trandate-lag(trandate) over (partition by emplid order by trandate)) * (24*60) as mins_diff
19        from t
20       )
21  where mins_diff <= 5
22* order by emplid, trandate
SQL> /
    EMPLID TRANDATE
         2 01/01/2010 09:22:00
SQL>