bookings(booking_id, room_id, start_at, end_at)

Return every pair of different bookings for the same room whose time ranges overlap. A booking that ends exactly when another starts does not overlap.

Return room_id, booking_id_1 and booking_id_2 with the smaller id first, so each clashing pair appears once, ordered by room then by both ids.

Two ranges overlap when each one starts before the other ends. Writing the condition that way is shorter and handles containment for free.

Tables

bookings

booking_id  room_id  start_at             end_at
----------  -------  -------------------  -------------------
1           100      2026-07-01 09:00:00  2026-07-01 11:00:00
2           100      2026-07-01 10:00:00  2026-07-01 12:00:00
3           100      2026-07-01 12:00:00  2026-07-01 13:00:00
4           200      2026-07-01 09:00:00  2026-07-01 17:00:00
5           200      2026-07-01 10:00:00  2026-07-01 11:00:00
6           300      2026-07-01 09:00:00  2026-07-01 10:00:00

Expected result

room_id  booking_id_1  booking_id_2
-------  ------------  ------------
100      1             2
200      4             5