RDIFF is used to find the right difference of the first Period expression with the second Period expression.
Assume the query runs on the following employee table where period1 and period2 are PERIOD(DATE) columns:
SELECT ename, period2 RDIFF period1 FROM employee;
The employee table contains:
ename period1 period2
----- ---------------------------- ----------------------------
Adams ('2005-02-03', '2006-02-03') ('2005-02-03', '2006-02-03')
Mary ('2005-04-02', '2006-01-03') ('2005-02-03', '2006-02-03')
Jones ('2001-01-02', '2003-03-05') ('2002-03-05', '2004-10-07')
Randy ('2006-01-02', '2007-03-05') ('2004-03-07', '2005-10-07')
Simon ? ('2005-02-03', '2005-07-27')
The result is:
ename (period2 RDIFF period1)
----- ----------------------------
Adams ?
Mary ('2006-01-03', '2006-02-03')
Jones ('2003-03-05', '2004-10-07')
Randy ?
Simon ?