I'm still not understanding key links very well. Please let me go through
an example.

BTW, I'm following Helen's advice on converting WHERE clause joins with
explicit joins when I come across them. I had mainly used where clause
joins to this point.

Example:

SELECT
A.AppointmentTime,
P.LastName,
P.LastName || ', ' || P.FirstName /*|| ' ' || P.MiddleInitial*/
PatientName,
P.ChartID,
P.HomePhone,
'Dr. ' || D.LastName DoctorName,
A.Notes,
APT.AUTOCOLOR
FROM
Appointment A
INNER JOIN PATIENT P ON (A.PATIENTID = P.PATIENTID)
INNER JOIN DOCTOR D ON (A.DOCTORID = D.DOCTORID)
LEFT JOIN APPOINTMENTTYPE APT ON (A.TYPEDESCRIPTION = APT.TYPEDESCRIPTION)
WHERE
A.AppointmentDate = :AppointmentDate
ORDER BY
A.AppointmentTime,
P.LastName

In this query there are no primary keys in the select. So I should use the
actual primary keys for the table?

So KeyLinks whould be:

APPOINTMENT.APPOINTMENTID

That would uniquely identify each record, but Helen said I need ALL of the
primary keys of the underlying table so would my keylinks then be:

APPOINTMENT.APPOINTMENTID
PATIENT.PATIENTID
DOCTOR.DOCTORID
APPOINTMENTTYPE.TYPEDESCRIPTION

Those are my primary keys on those tables.

In the KeyLinks demo program there was something like:

CUSTOMER.ORDERID = ORDER.ORDERID

I'm not sure I understand what this means as the query was a simple select
(select * from customer) in the demo app.

Also I still don't understand why this is necessary because it's working
without the key links?