time_to_millis function
Applies to: 
Databricks SQL Databricks Runtime 18.3 and above
Returns the number of milliseconds since midnight for a TIME value.
Syntax
time_to_millis(expr)
Arguments
expr: A TIME expression.
Returns
A BIGINT.
Examples
SQL
> SELECT time_to_millis(TIME'14:30:00.5');
52200500
> SELECT time_to_millis(TIME'00:00:00');
0