How to count how many doctors are booked by each patient?

Question

I need the results to look like:

PatientID   Doctors
Patient1    3
Patient2    2
Patient3    1

The booked table looks like this

Answer 1

You are looking for count(distinct):

select b.PatientID, count(distinct b.DoctorID) as NumDoctors
from Bookings b
group by b.PatientID;