The Microsoft Jet database engine contains a sophisticated query processor that’s responsible for query execution. There is, however, much more to the query engine than just a query processor. The query engine also contains a sophisticated query optimizer that takes any given query as its input and determines the fastest join strategy for executing that query.
A query may be internally optimized to yield a more efficient join strategy, but this is all done without intervention from the user. The goal of the query engine is to take any query, no matter how poorly structured, and execute that query in the most efficient manner.