Increment Oracle time in varchar field by a certain amount?

We have times stored in an Oracle varchar(5) field.

Times stored using HH24:MI (ie: 22:30, 10:15).

How can we run a query that will increase or decrease these times by a certain amount?开发者_StackOverflow社区 Ie: increase by one hour or decrease by 45 minutes.

you could use the built-in date (and interval -- thanks Alex for the link) calculation:

to_char(to_date(:x, 'hh24:mi') + INTERVAL :y MINUTE,'hh24:mi')

for instance:

SQL> WITH my_data AS (
  2     SELECT '12:15' t FROM dual
  3     UNION ALL SELECT '10:30' FROM dual
  4  )
  5  SELECT t, 
  6         to_char(to_date(t, 'hh24:mi') + INTERVAL '15' MINUTE,'hh24:mi')"t+15"
  7    FROM my_data;

T     t+15
----- -----
12:15 12:30
10:30 10:45

The functions to convert from/to date and char are TO_DATE() and TO_CHAR():

SELECT
    TO_DATE('31/12/2001 23:55:00', 'DD/MM/YYYY HH24:MI:SS') AS "DATE",
    TO_CHAR(CURRENT_TIMESTAMP, 'DD/MM/YYYY HH24:MI:SS') AS "CHAR"
FROM DUAL

So you can do:

SELECT
    TO_DATE('23:45', 'HH24:MI'),
    TO_DATE('23:45', 'HH24:MI') + INTERVAL '45' MINUTE,
    TO_CHAR(TO_DATE('23:45', 'HH24:MI') + interval '45' MINUTE, 'HH24:MI')
FROM DUAL

There're possibly other better ways to do it (I'm not sure this will work as expected if ran when DST is about to start) but I'm still learning :)