Converting time difference to a given format in Oracle

Question

How do I convert EVENT_DATE_B - EVENT_DATE_A which is a number of days to string with HH:MM format?

Answer 1

Another approach (one query can be on different days):

with tt as (
   select numToDsinterval((EVENT_DATE_B - EVENT_DATE_A ), 'DAY') dsint 
     from t)
select (extract(day from dsint)*24)+extract(hour from dsint) || 
       ':' ||extract(minute from dsint)
from tt

Here is a sqlfiddle demo