# Chapter 10. Type Conversion

Table of Contents

10.1. Overview

10.2. Operators

10.3. Functions

10.4. Value Storage

10.5. UNION, CASE, and Related Constructs

10.6. SELECT Output Columns

SQL statements can, intentionally or not, require the mixing of different data types in the same expression.PostgreSQL has extensive facilities for evaluating mixed-type expressions.

In many cases a user does not need to understand the details of the type conversion mechanism. However, implicit conversions done by PostgreSQLcan affect the results of a query. When necessary, these results can be tailored by using explicit type conversion.

This chapter introduces the PostgreSQLtype conversion mechanisms and conventions. Refer to the relevant sections in Chapter 8 and Chapter 9for more information on specific data types and allowed functions and operators.