SQL in a Nutshell, 4th Edition

Chapter 4. Reading Your Data

In this chapter, we will explore the key SQL statements and clauses needed to extract information from your database. You will learn about the fundamental SELECT statement and the various subclauses you can use within it to select data and aggregate data into subtotals. By the end of this chapter, you will understand the concepts of JOIN operations, SET operations, aggregation, window operations, common table expressions, and subqueries. You will also know how to combine these effectively to query any data in the core database platforms.

How to Use This Chapter

When researching a command in this chapter:

1. Read “SQL Platform Support”.

2. Check Table 4-1.

3. Look up the specific SQL statement, check the syntax, and read the “Keywords,” “Rules at a glance,” and “Programming tips and gotchas” sections and read the section on the standard for SQL syntax and description. Do this even if you are looking for a specific platform implementation.

4. Finally, read the platform-specific implementation information.

You will note that the entry for a given platform implementation does not duplicate information on any clauses that do not differ from the standard. So, it is possible that you will need to flip between the descriptions for a vendor variation and the SQL standard to cover all possible details of that command.

In our discussions of MySQL, we will also include MariaDB, a fork of MySQL. For the most part, MySQL and MariaDB provide fully code-compatible syntax. ...