In this chapter, you learned how to use aggregate functions to group and summarize data. Aggregate functions include math functions such as AVG, SUM, COUNT, MIN, and MAX. They also include statistical functions such as STDDEV and VARIANCE.
You learned how to use GROUP BY with and without aggregate functions to summarize data. You also learned how to filter summarized data with the HAVING clause. Then, you learned the difference between the HAVING and WHERE clauses.
Finally, you learned how MySQL actually executes your query clauses. It's not about the order you write the clauses in, but writing them in a different order that explains why you can't use aliases in all the clauses of the SQL statement.
In the next chapter, you will learn how to use advanced querying techniques. By the end of the next chapter, you will be able to understand what types of subqueries...