Return date/times outside of a date/time range

[skhanal]

Since you are trying to generate a list of time slots which does not exist in the table you are querying, you may have to build an intermediate table or inline view to accomplish this.

For example for the give time range, you can build an inline view with all time slots (make it half hour only to simplify it), then intersect this with the unavailable time slots data from the table.

Does the time slots start on the hour or half hour only?. If not it may complicate your query further. In that case it may be better to write a stored procedure instead.