Xem xét việc sử dụng cái được gọi là CTE (biểu thức bảng chung) (Tham khảo tài liệu MSDN):
;with cteAppointments as (
select AppointmentID, PersonID, PrevAppointmentID
from Appointments
where PrevAppointmentID is null
union all
select a.AppointmentID, a.PersonID, a.PrevAppointmentID
from Appointments a
inner join cteAppointments c
on a.PrevAppointmentID = c.AppointmentID
)
select AppointmentID, PrevAppointmentID
from cteAppointments
where PersonID = xxx
