List all the physician names.
select name from physician
Find the names of the physicians who took appointments.
select t2.name from appointment as t1 join physician as t2 on t1.physician = t2.employeeid
Then what are the names of physicians who never took any appointment?
select name from physician except select t2.name from appointment as t1 join physician as t2 on t1.physician = t2.employeeid