SQL Time Overlap Analysis

Analyze how many minutes where a single interview room had two or more interviewers at once using start_time and end_time.

Assume each row represents one interviewer scheduled in a room. Treat intervals as half-open, so an interviewer ending exactly when another begins does not create overlap. Include rooms with no overlapping time and ignore rows with missing or invalid timestamps.

Output

1. One row per room with valid or recorded scheduling data.
2. Columns: room_name, overlapping_minutes.
3. Report total minutes during which at least two interviewers were present, ordered by room_name ascending.