Reference to composite primary key in Access 2007
I have looked around and found some questions similar but they were for SQL Server instead.
Here is a small database structured I have create just to show you the relationships I want to model. Basically it's quite simple, each year has 12 periods and an instance of period-year cannot occur twice (period 9 year 2012 cannot occur more than once ever).
So I thought that the best way to model this would be to have a table period with only one field with values from 1-12, a table year following the same logic (2011,2012...) and since it is an N-to-N relationship I have created the period_by_year table which joins them to be used by rpt_maintenance_kpi. Now the tricky part is that in order to make each combination unique, I have made the both period_no and year_no part of a composite primary key. This solves the problem elegantly in my opinion, but then I am stuck on how to reference this composite primary key from the rpt_maintenance_kpi (or any other table for that matter). I have tried making two joins but this does not seem to work (creates a second rpt_maintenance_kpi table and I believe this will not do what I want to do).
So how could I handle a foreign key to a composite primary key ?
Many thanks in advance.
Answer
Create the Year or Period relationship with Maintenance, then either double-click the relationship line to edit the relationship or drag the second part (year or period accordingly) to Maintenance and choose Yes when asked if you want to edit the relationship. You can now add the second line, like so:
