In this section, we're going to go over more of the SQL programming language.
We're going to cover aggregate functions, join statements, and subqueries.
Aggregate functions allow you to take multiple values in a set and resolve them to a single value,
like a max or an average.
Join statements take advantage of the relationships in a relational database and allow you to query
multiple tables in a single query.
Instance subqueries allow you to embed SQL statements within other SQL statements to further refine
your query results.
So let's get started.