MySQL add 12 hours to a time field

Question

I need to add 12 hours to a MySQL TIME field (not DATETIME) and I'm having trouble.

UPDATE `events` 
SET start_time = DATE_ADD(start_time, INTERVAL 12 HOUR)
WHERE `start_time` < '11:00:00'

returns with no errors but doesn't change anything, I think because start_time is a TIME field.

UPDATE `events` 
SET start_time = start_time + '12:00:00'
WHERE `start_time` < '11:00:00'

adds 12 seconds.

Answer 1

Try using ADDTIME instead of DATE_ADD. You could do SET start_time = ADDTIME(start_time, '12:00:00')

Answer 2

UPDATE `events` 
SET start_time = start_time + INTERVAL 12 HOUR
WHERE `start_time` < '11:00:00'

The MySQL functions that accept INTERVAL arguments are mostly unnecessary; you can just add and subtract intervals with + and -.