Compound keys used to be the only way to match multiple pairs of fields in a single relationship. You define a stored calculation field that returns text with an expression such as:
customerIDfield & " " & EffectiveDateField. You'd match this to a simple text field in the daughter table if you plan to use the relationship to create the related records or a similar calculation field if you did not plan to use the relationship in this way.
Now we have a way that is usually better. We simply match up multiple pairs of fields in the same relationship.
Enter manage | Database | relationship
Drag from the customer ID field to its matching ID field in a different table. Now drag from the effective date field to the matching date field in the other relationship.
You've now based your relationship on multiple pairs of fields. To see more relationship details, double-click the relationship line linking the two tables.
The only draw back to this approach is that sometimes you get very confusing relationship graphs if you have a number of these relationships with some key fields in common.
In a similar vein, maybe someone will be so helpful as to suggest a way to make a 'Compound Key' that is unique, The above suggestion would work, but, does not provide a uniqueness.
in my case, the unique key should consist of :
Year (really just a number 1 - 6)
Param2 (Text from lookup table)
Other stuff : eg
value ... etc