You can add all the right indexes and still end up with slow queries. The problem is rarely the index itself. It's how the query is written. A single function call in a WHERE clause, a mismatched data type, or a careless SELECT * can force the database to ignore your indexes entirely and fall back to a full table scan.

This chapter covers the most common anti-patterns that silently kill query performance, and the optimization techniques that fix them.

Insert these rows to follow along:

Create the indexes referenced throughout this chapter: