Question

I have a table for appointments containing dates and Pupil IDs which I am trying to get to automatically duplicate on a weekly basis. I want to run a query which detects if each appointment has a copy of itself a week ahead, so original data was:

PupilID   Date
1         10th May
2         16th May

After the query,

PupilID   Date
1         10th May
2         16th May
1         17th May
2         23rd May

I am trying to use the following with no luck. Suggestions would be much appreciated. I have code doing the job already, but it is getting really slow.

INSERT timetable (pupil_id,date) SELECT timetable.pupil_id AS pupil_id2,DATE_ADD(timetable.date,INTERVAL 14 DAY) AS date2 FROM timetable WHERE  NOT EXISTS pupil_id2=timetable.pupil_id AND date2=timetable.date;

Answer 1

Would it be sufficient to check whether there was a future appointment at all?

Give this a shot:

insert into timetable (pupil_id,date)
select t.pupil_id, DATE_ADD(t.date, INTERVAL 14 DAY)
from timetable t 
where not exists (select 1 from timetable
                         where pupil_id = t.pupil_id
                         and date > t.date)

You could change the last clause to specifically check for the 14 days ahead:

where not exists (select 1 from timetable
                         where pupil_id = t.pupil_id
                         and date = DATE_ADD(t.date, INTERVAL 14 DAY))        

I recommend the first query though.