In this chapter, you learned to use SELECT statements to project the data needed and filter data with WHERE, LIMIT, IN/EXISTS. Then, we introduced different joins to link datasets together, as well as the dataset operations UNION and UNION ALL. After going through this chapter, you should be able to use the SELECT statement with different WHERE conditions, LIMIT, DISTINCT, and complex subqueries. You should be able to understand and use different types of JOIN statements to link the different datasets horizontally or UNION them vertically.

In the next chapter, we will talk about the details of data exchanging, ordering, and transforming, as well as transactions in HQL.