Finding records that are not in a query based on several tables

[Phil R]

I have students (one table) doing subjects (second table) joined in a third
table (named reports, because each student will receive a report in each
subject for which they are enrolled) which uniquely defines all
student/subject combinations. Then I have fourth table (called timetable for
obvious reasons) that is linked with the above three to show when each of the
above subjects are running in a week. What I want to do is identify all
students who are not actually studying anything at a particular time on the
timetable. This cannot be done simply by using the "null" criteria in the
student or subject column. It is really a combined 'null' that I am wanting
to query. I really want to know, for any record (time slot) from table four,
which students do not have a combination in table three.
Hope this makes sense. I've not used this forum before!

 

[Jeff Boyce]

Phil

You described how your many-to-many relationship of students and subjects
are handled in a third table (?your "reports"). You did not describe how
you related these three to your "timetable" table, just that they are.

Knowing the relationship would help in suggesting how to find students who
are not studying a subject during a timeframe...