Chapter 18 introduced the concept of an inverted index to prevent the database system from performing a full column scan every time a query searches for a predicate in the column. However, maintaining an index is expensive and consumes additional memory. So the decision to use an index should be made carefully, balancing all the pros and cons an index would bring in the particular situation. This chapter discusses how to speed up a full column scan despite adding an index to it. Chapter 17 introduced parallelism as a means to parallelize the execution of database operations. In this chapter, we present a detailed description of how parallelism can be used to speed up the execution of a SELECT operation.