Indexes and Optimizing Techniques

In Chapter 30, we presented table constraints such as PRIMARY KEY and CHECK. In that same chapter, we introduced unique indexes as a way to enforce a PRIMARY KEY constraint. In addition to using indexes to enforce constraints, you can use indexes to boost the performance of queries significantly by reducing the amount of time needed to retrieve rows from a table instead of reading every row in the table to find the row or rows you are looking for. However, too many indexes on a table can be just as bad as not enough.