The TIME_DIFF function allows you to find the difference between 2 TIMEs in the specified part interval.
TIME_DIFF(time_expression_a, time_expression_b, part)
Where part can be any of the following:
SELECT TIME '15:30:00' AS first_time, TIME '14:35:00' AS second_time, TIME_DIFF(TIME '15:30:00' , TIME '14:35:00', MINUTE) AS difference
A common SQL query WHERE clause is to just pull the data for the last n seconds. In this case, we can make use of TIME_DIFF and CURRENT_TIME:
SELECT time, TIME_DIFF(CURRENT_TIME(), time, SECOND) AS seconds_since FROM ( SELECT TIME '13:05:00' AS time UNION ALL ( SELECT TIME '13:05:00' AS time) UNION ALL ( SELECT TIME '13:05:00' AS time) ) AS table_3 WHERE (TIME_DIFF(CURRENT_TIME(), time, SECOND) <= 30)
This one is all too common. If you're using TIME, you'll need to make sure both of your TIMEs are indeed TIME data types, and not DATEs or DATETIMEs. It's usually easy enough to add a CAST(timestamp_col as TIME) to your function:
TIME_DIFF(CAST('2020-01-01 03:22:01' as TIME),'03:04:00', HOUR) hours_diff