SQL query question: SELECT … NOT IN

Question

I am sure making a silly mistake but I can\'t figure what:

In SQL Server 2005 I am trying select all customers except those who have made a reservation before 2 AM.<

Answer 1

SELECT Reservations.idCustomer FROM Reservations (nolock)
LEFT OUTER JOIN @reservations ExcludedReservations (nolock) ON Reservations.idCustomer=ExcludedReservations.idCustomer AND DATEPART(hour, ExcludedReservations.insertDate) < 2
WHERE ExcludedReservations.idCustomer IS NULL AND Reservations.idCustomer IS NOT NULL
GROUP BY Reservations.idCustomer

[Update: Added additional criteria to handle idCustomer being NULL, which was apparently the main issue the original poster had]