I was once asked by a fellow colleague if it was possible to have an SQL statement that would not allow employees from being registered to events that occur simultaneously.
Consider a database that stores a list of persons and a list of events. Employees would eventually be registered as event attendees. It is possible that multiple events occur at the same time and therefore it is required that the SQL statement prevent any persons from being registered as attendees of conflicting events. It was required that the solution be all in one SQL statement for some reason whatsoever.
The SQL solution is found attached together with a supporting report! As always all feedback and queries are welcome!