F_AGEINSECONDSN

Entrypoint ageinsecondsnull compatible with UTF-8

   Input      TIMESTAMP     (older) date optionally time 1
              TIMESTAMP     (newer) date optionally time 2
   Output     INTEGER       difference in (integer) seconds between timestamp 1 and timestamp 2

   For compatibility reasons:
   If date 2 < date 1 the result is negative. The correct result had been 0 than there is no negative age!
   Use F_AGEIN...N or F_...BETWEEN if you don't want a negative age.
   TestSQL
   SELECT 3 AS ISCORRECT, F_AGEINYEARS('01.01.2005 15:01:21','01.10.2008 15:01:01') FROM RDB$DATABASE;
   SELECT -3 AS ISCORRECT, F_AGEINYEARS('01.01.2005 15:01:21','01.10.2002 15:01:01') FROM RDB$DATABASE;
   SELECT NULL AS ISCORRECT, F_AGEINYEARS(NULL, NULL) FROM RDB$DATABASE;
   SELECT 9 AS ISCORRECT, F_AGEINMONTHS('01.01.2005 15:01:21','01.10.2005 15:01:01') FROM RDB$DATABASE;
   SELECT -9 AS ISCORRECT, F_AGEINMONTHS('01.10.2005 15:01:21','01.01.2005 15:01:01') FROM RDB$DATABASE;
   SELECT NULL AS ISCORRECT, F_AGEINMONTHS(NULL, NULL) FROM RDB$DATABASE;
   SELECT 20 AS ISCORRECT, F_AGEINWEEKS('01.01.2005 15:01:21','15.05.2005 15:01:21') FROM RDB$DATABASE;
   SELECT -33 AS ISCORRECT, F_AGEINWEEKS('01.01.2006 15:01:21','15.05.2005 15:01:21') FROM RDB$DATABASE;
   SELECT NULL AS ISCORRECT, F_AGEINWEEKS(NULL, NULL) FROM RDB$DATABASE;
   SELECT 10 AS ISCORRECT, F_AGEINDAYS('01.10.2005 15:01:03','11.10.2005 15:04:03') FROM RDB$DATABASE;
   SELECT -20 AS ISCORRECT, F_AGEINDAYS('01.10.2005 15:01:03','11.09.2005 15:04:03') FROM RDB$DATABASE;
   SELECT 3 AS ISCORRECT, F_AGEINHOURS('01.10.2005 15:01:03','01.10.2005 18:01:03') FROM RDB$DATABASE;
   SELECT NULL AS ISCORRECT, F_AGEINDAYS(NULL, NULL) FROM RDB$DATABASE;
   SELECT 14 AS ISCORRECT, F_AGEINMINUTES('01.10.2005 15:01:03','01.10.2005 15:15:03') FROM RDB$DATABASE;
   SELECT NULL AS ISCORRECT, F_AGEINHOURS(NULL, NULL) FROM RDB$DATABASE;
   SELECT 14 AS ISCORRECT, F_AGEINMINUTES('01.10.2005 15:01:03','01.10.2005 15:15:03') FROM RDB$DATABASE;
   SELECT NULL AS ISCORRECT, F_AGEINMINUTES(NULL, NULL) FROM RDB$DATABASE;
   SELECT 20 AS ISCORRECT, F_AGEINSECONDS('01.01.2005 15:01:01','01.01.2005 15:01:21') FROM RDB$DATABASE;
   SELECT NULL AS ISCORRECT, F_AGEINSECONDS(NULL, NULL) FROM RDB$DATABASE;