During the join optimization phase, the Query Processor calculates:
- An Access Path for each table that is referenced in your query
- Every possible permutation (Join Order) for the tables in your query.
When referred to collectively, the access paths and join order for a single permutation are called an Access Plan.
The Query Processor will calculate an access plan for every permutation, and will also calculate the cost of each access plan. The access plan with the lowest cost is the access plan that will be used to obtain the values for your query. This is called the Final Access Plan.