How to get the time difference between two date columns?

Oracle allows two date values to be subtracted from each other returning a numeric value indicating the number of days between the two dates (may be a fraction). This example will show how to relate it back to a time value.

Let's investigate some solutions. Test data:

SQL> CREATE TABLE dates (date1 DATE, date2 DATE);
Table created.
SQL>
SQL> INSERT INTO dates VALUES (SYSDATE, SYSDATE-1);
1 row created.
SQL> INSERT INTO dates VALUES (SYSDATE, SYSDATE-1/24);
1 row created.
SQL> INSERT INTO dates VALUES (SYSDATE, SYSDATE-1/60/24);
1 row created.
SQL> SELECT (date1 - date2) FROM dates;
DATE1-DATE2
-----------
1
.041666667
.000694444

Solution 1:
---------------------------------------------

SQL> SELECT floor(((date1-date2)*24*60*60)/3600)
2 || ' HOURS ' ||
3 floor((((date1-date2)*24*60*60) -
4 floor(((date1-date2)*24*60*60)/3600)*3600)/60)
5 || ' MINUTES ' ||
6 round((((date1-date2)*24*60*60) -
7 floor(((date1-date2)*24*60*60)/3600)*3600 -
8 (floor((((date1-date2)*24*60*60) -
9 floor(((date1-date2)*24*60*60)/3600)*3600)/60)*60) ))
10 || ' SECS ' time_difference
11 FROM dates;
TIME_DIFFERENCE
--------------------------------------------------------------------------------
24 HOURS 0 MINUTES 0 SECS
1 HOURS 0 MINUTES 0 SECS
0 HOURS 1 MINUTES 0 SECS


Solution 2:
-----------------------

If you don't want to go through the floor and ceiling maths, try this method.

SQL> SELECT to_number( to_char(to_date('1','J') +
2 (date1 - date2), 'J') - 1) days,
3 to_char(to_date('00:00:00','HH24:MI:SS') +
4 (date1 - date2), 'HH24:MI:SS') time
5 FROM dates;
DAYS TIME
---------- --------
1 00:00:00
0 01:00:00
0 00:01:00