Optionally, you can complete additional practice with SQL using either of the following sites.
SQLZoo
Exercises one through eight are as far as you need to go, at this time:
SQL Murder Mystery
There’s been a Murder in SQL City! The SQL Murder Mystery is designed to be both a self-directed lesson to learn SQL concepts and commands and a fun game for experienced SQL users to solve an intriguing crime.
TIP
Even if you don’t try this resource, their walkthrough of SQL basics is really good.