Indexes usage in Jet and SQL Server

While working on a Access/SQL Server project I was faced with a difference in indexes behavior in Jet and SQL Server table. Say you have Order and OrderDetails tables. Each table has a surrogate primary key with autonumber or identity. You have a relationship between these tables. Now you make a query, join both table and run it. Jet uses a hidden index from relation in OrderDetails, but SQL Server – no and SQL Server query works much slower! So you have to add a new index for many side field of relation.