how to add 30 minutes in last value of return query using oracle?

My query is

Select class_time from tableA

which produces:

0200AM
0230AM
0300AM
0330AM
0400AM

i want above result as

0200AM
0230AM
0300AM
0330AM
0400AM
0430AM

Answer

Assuming you are storing the times in a DATE data type (which always has year, month, day, hour, minute and second components) then add an INTERVAL literal to the maximum value from the table:

SELECT class_time from tableA
UNION ALL
SELECT MAX( class_time ) + INTERVAL '30' MINUTE FROM tableA

or add a fraction of a day:

SELECT class_time from tableA
UNION ALL
SELECT MAX( class_time ) + 30 / ( 24 /* hours */ * 60 /* minutes */ )  FROM tableA

Output:

| CLASS_TIME          |
| :------------------ |
| 2019-12-16 02:00:00 |
| 2019-12-16 02:30:00 |
| 2019-12-16 03:00:00 |
| 2019-12-16 03:30:00 |
| 2019-12-16 04:00:00 |
| 2019-12-16 04:30:00 |

---

If your times are stored as strings then convert them to a date, add 30 minutes and then convert back to a string:

SELECT class_time from tableB
UNION ALL
SELECT TO_CHAR(
         MAX( TO_DATE( class_time, 'HH12:MI AM' ) )
         + INTERVAL '30' MINUTE,
         'HH12:MI AM'
       )
FROM   tableB

Output:

| CLASS_TIME |
| :--------- |
| 02:00 AM   |
| 02:30 AM   |
| 03:00 AM   |
| 03:30 AM   |
| 04:00 AM   |
| 04:30 AM   |

db<>fiddle here