The TIME_TO_SEC function returns the seconds in the range of 0 to 86,399 from specified argument. You can specify the TIME, TIMESTAMP, or DATETIME type; the value is returned in INTEGER type.
TIME_TO_SEC(time)
SELECT TIME_TO_SEC('23:00:00');
time_to_sec('23:00:00')
==========================
82800
SELECT TIME_TO_SEC('2010-10-04 23:00:00');
time_to_sec('2010-10-04 23:00:00')
=====================================
82800
SELECT TIME_TO_SEC('2010-10-04 23:00:00.1234');
time_to_sec('2010-10-04 23:00:00.1234')
==========================================
82800
SELECT TIME_TO_SEC('2010-01-01');
ERROR: Conversion error in time format.