format interval with to_char

Question

Following SQL command

select TO_CHAR(NVL(arg1 - arg2, TO_DSINTERVAL(\'0 00:00:00\'))) from table1

produces a result of the format: +0000000

Answer 1

Slight case of thread necromancy, however I came across this question while searching for how to format an interval, so I thought it was worth adding this comment.

From the Oracle documentation, adding a timestamp to an interval results in a timestamp, so by adding a constant timestamp with zero time elements you can then use the standard to_char format elements for datetime ...

SELECT TO_CHAR( TIMESTAMP'1969-12-31 00:00:00' + TO_DSINTERVAL('0 00:03:01.954321'),
  'HH24:MI:SS.FF3' ) FROM dual;

However, there is an issue if you intervals could be greater than a day. There is no format element for days that will yield 0. "DDD" is day of the year, so would be 365 in the example above, or 1 or more if the interval was greater then a day. This is fine as long as your intervals are less than 24 hours though.

Should add this is on 11g so may well not have be applicable to the OP.