Limit to two results for each individual ID - mysql

Question

How would I return two results for each individual meeting.id?
I've tried things like Row_Count() and Rank() but they seem to cause syntax errors.
This is my query which I need adapting to show the two results per meeting.id.
SELECT meeting_appointment.* FROM `meeting`
INNER JOIN meeting_appointment ON (
meeting_appointment.meeting_id = meeting.id AND meeting_appointment.pupil_id = 0 AND meeting_appointment.guardian_id = 0 AND meeting_appointment.deleted = 0
)
WHERE (
meeting.grade_id = "-1" OR meeting.grade_id IN ('87')
)
AND meeting.startTime < '2016-10-06 14:00:00' + INTERVAL 1 HOUR AND meeting.startTime > '2016-10-06 14:00:00' - INTERVAL 1 HOUR
GROUP by meeting_appointment.id
ORDER BY meeting_appointment.startTime ASC

Answer 1

If your meeting_appointment.id are consecutive then this should show the first two
meeting_appointment.id per meeting.id:
SELECT meeting_appointment.* FROM `meeting`
INNER JOIN meeting_appointment ON (meeting_appointment.meeting_id = meeting.id)
WHERE (meeting.grade_id = "-1" OR meeting.grade_id IN ('87'))
AND meeting.startTime < '2016-10-06 14:00:00' + INTERVAL 1 HOUR AND meeting.startTime > '2016-10-06 14:00:00' - INTERVAL 1 HOUR
AND meeting_appointment.pupil_id = 0
AND meeting_appointment.guardian_id = 0
AND meeting_appointment.deleted = 0
AND NOT EXISTS
(SELECT 1 FROM meeting_appointment ma WHERE ma.id<meeting_appointment.id-1
AND ma.pupil_id = 0
AND ma.guardian_id = 0
AND ma.deleted = 0
)
GROUP by meeting_appointment.id
ORDER BY meeting_appointment.startTime ASC
If you meeting_appointment.id are just random or non-numeric then it might need some tweaks but in order to code those teaks we'll need to know a bit more about the schema.

Answer 2

You don't have an aggregate function, so GROUP BY is redundant. Remove that, and add a LIMIT clause, and you should be good to go:
SELECT ma.*
FROM meeting m
INNER JOIN meeting_appointment ma ON ma.meeting_id = m.id
WHERE m.grade_id IN ('-1','87')
AND ma.pupil_id = 0
AND ma.guardian_id = 0
AND ma.deleted = 0
AND m.startTime < '2016-10-06 14:00:00' + INTERVAL 1 HOUR
AND m.startTime > '2016-10-06 14:00:00' - INTERVAL 1 HOUR
ORDER BY ma.startTime ASC
LIMIT 2;
You could also use BETWEEN for the datetime column.