Summary

In this chapter, we learned that SQL aggregate functions provide an efficient, flexible way to calculate summary values in SQL query result sets. We discovered that the GROUP BY clause will separate the results of a SELECT query into one or more row groups to support the design and execution of queries with aggregate functions. We saw that the HAVING clause provides a pinpoint way to filter aggregate function calculations. Although they're similar, we learned about the differences between WHERE and HAVING clauses. Finally, we saw that when we use OVER and PARTITION BY in creative ways, MySQL will efficiently expand the range of problems it can solve for us. We can also order the items with a group using the RANK and DENSE RANK functions. In the next chapter, we will look at some advanced features of SQL programming.