SQL for MySQL Developers: A Comprehensive Tutorial and Reference

Chapter 14. Combining Table Expressions

14.1 Introduction

Section 6.4 introduced the term compound table expression. Set operators allow us to combine multiple table expressions into one compound table expression. Examples in Section 6.4 and several other chapters used the set operator called UNION, which places results of table expressions underneath each other. MySQL supports other set operators besides the UNION operator:

• UNION

• UNION DISTINCT

• UNION ALL

Chapter 6, “SELECT Statements, Table Expressions, and Subqueries,” defined the table expression and the compound table expression. However, that chapter mentions only the UNION operator. Now we extend that definition with the complete set of set operators.

Definition

<table expression> ...