In the previous chapter, we looked at strategies to identify potential indexes for your databases. That, though, is often only half the story. Once the indexes have been created, you would expect performance within the database to improve, leading you then to the next bottleneck. Unfortunately, coding practices and selectivity can sometimes negatively influence the application of indexes to queries. And sometimes how the database and tables are being accessed will prevent the use of some of the most beneficial indexes in your databases.