In this chapter, you learned how to access different types of databases from R. We introduced the basic usage of relational databases such as SQLite and non-relational databases such as MongoDB and Redis. With the understanding of major differences in their functionality and feature sets, we need to choose an appropriate database to work with in our projects according to our purpose and needs.

In many data-related projects, data storage and data importing are the initial steps, but data cleaning and data manipulation cost most of the time. In the next chapter, we will move on to data-manipulation techniques. You will learn about a number of packages that are specially tailored for handy but powerful data manipulation. To better work with these packages, we'll need a better understanding of how they work, which requires the sound knowledge introduced in the previous chapters.