Questo dovrebbe farlo per te:
select
m.AppointmentTimeID,
m.AppointmentDate,
coalesce(sum(ap.NumberOfApplicants),0) as NoOfApplicants
from (
-- just basically doing a cross to get all time/date combinations
select distinct d.AppointmentTimeID, a.AppointmentDate
from tbl_appointments a, tbl_appointmentschedule_details d
) m
left join tbl_appointments ap
on ap.AppointmentTimeID = m.AppointmentTimeID
and ap.AppointmentDate = m.AppointmentDate
where m.AppointmentDate between '2015-10-16' and '2015-10-17'
group by m.AppointmentDate, m.AppointmentTimeID
order by m.AppointmentDate, m.AppointmentTimeID
Esempio SQLFiddle:http://sqlfiddle.com/#!9/1e632/15
Results:
| AppointmentTimeID | AppointmentDate | NoOfApplicants |
|-------------------|---------------------------|----------------|
| 22 | October, 16 2015 00:00:00 | 0 |
| 23 | October, 16 2015 00:00:00 | 3 |
| 24 | October, 16 2015 00:00:00 | 3 |
| 25 | October, 16 2015 00:00:00 | 1 |
| 26 | October, 16 2015 00:00:00 | 0 |
| 22 | October, 17 2015 00:00:00 | 4 |
| 23 | October, 17 2015 00:00:00 | 0 |
| 24 | October, 17 2015 00:00:00 | 0 |
| 25 | October, 17 2015 00:00:00 | 0 |
| 26 | October, 17 2015 00:00:00 | 0 |
Per velocizzare un po' le cose, potresti trarre vantaggio da un po' di indicizzazione:
create index idx_tbl_appointments_apptdate_timeid on tbl_appointments(AppointmentDate, AppointmentTimeID);
create index idx_tbl_appointmentschedule_details_TimeID on tbl_appointmentschedule_details(AppointmentTimeID);
Modifica della query:
select
m.AppointmentTimeID,
m.AppointmentDate,
coalesce(sum(ap.NumberOfApplicants),0) as NoOfApplicants
from (
select distinct AppointmentTimeID, AppointmentDate
from (select distinct AppointmentTimeID from tbl_appointmentschedule_details) one
cross join
(select distinct AppointmentDate from tbl_appointments
where AppointmentDate between '2015-10-16' and '2015-10-17') two
) m
left join tbl_appointments ap
on ap.AppointmentTimeID = m.AppointmentTimeID
and ap.AppointmentDate = m.AppointmentDate
where m.AppointmentDate between '2015-10-16' and '2015-10-17'
group by m.AppointmentDate, m.AppointmentTimeID
order by m.AppointmentDate, m.AppointmentTimeID
Esempio SQLFiddle:http://sqlfiddle.com/#!9/0de6d7/1
Si noti che ho aggiunto l'intervallo di date in due posizioni in questa query. Guarda come si comporta questa query per te.
