In chapter 2, we used fairly simple conditions in the
where clause. In this chapter, we discuss how to combine several of these simple conditions into a compound condition. This is particularly important when we are handling tables with many rows. It allows us to specify the particular set of rows we want.
This chapter also discusses several other important topics. You should read this chapter quickly and make sure you do not get bogged down in any part of it. The topics themselves are not really part of SQL. Rather, these are general programming topics that could trip you up along the way if you are not aware of them.
If your main goal is to learn SQL, I recommend that you read the chapter once ...