## Chapter 10. Type Conversion

**Table of Contents**

[10.1. Overview](typeconv-overview.html)

[10.2. Operators](typeconv-oper.html)

[10.3. Functions](typeconv-func.html)

[10.4. Value Storage](typeconv-query.html)

[10.5. `UNION`, `CASE`, and Related Constructs](typeconv-union-case.html)

[10.6. `SELECT` Output Columns](typeconv-select.html)

[]()

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](datatype.html) and [Chapter 9](functions.html)for more information on specific data types and allowed functions and
operators.

