You can't do it the way you've describe.
With a Group
and Staff
table, if you want a many-to-many relationship, you do (as you state) have to have a joining table (GroupStaff
). However, you can't really create the relationships on either the Group
or Staff
tables.
You have to create new rows in the GroupStaff
table. You can do this manually on row at a time, of if I'm creating a an app, I'll generally have a form with two sub forms. The parent form would be bound to Group
in this case, and the subforms would be bound to Staff
and GroupStaff
respectively. You can then add controls (buttons) to add records to the GroupStaff
table base on what records were selected in the Group
form and the Staff
subform.
The GroupStaff
subform would also be filtered to show only the records associated with the group currently on the parent from.