In this chapter, we discussed views and virtual columns. These topics are logically related, because views can be considered as virtual tables.

We examined views and learned how to manage or query them. We discussed their limitations, and some of the purposes for which they could be used. In particular, we learned how they can improve the database security.

Then we discussed virtual columns. This term includes both VIRTUAL and PERSISTENT columns; the former are calculated on-the-fly when needed, and the latter are stored on disk. We discussed how this feature can help us with some practical examples. The examples also showed how PERSISTENT columns can be used to build useful indexes, or to create powerful UNIQUE checks.

In the next chapter, we will talk about dynamic columns and understand the kind of problems they can solve.