I have the following tables (I left out fields that don't apply to this question).

Employees, Stores, and Groups. Each employee can belong to one or more Stores, and each Store is in one Group

Employees
EmployeeId Number
Certified DateTime

EmployeeStores
EmployeeStoreId Number
EmployeeId Number
StoreId Number

Stores
StoreId Number
GroupId Number


I need to produce a query that displays the percentage of the Certified field completed in the Employees table by Group. So, assuming Group A, Group B, and Group C, the result set should have:

Group A 13
Group B 42
Group C 21
Other 24

I'm not sure how to do this kind of calculation in SQL, and since I'm very new to Access, I could use some.

Thank you