Function Declaration and Definition

13.36 Function Declaration and Definition

Before invoking a function, you must declare and define it. You can either declare it first (with function_declaration) and then define it later in the same block, subprogram, or package (with function_definition) or declare and define it at the same time (with function_definition).

A function is a subprogram that returns a value. The data type of the value is the data type of the function. A function invocation (or call) is an expression, whose data type is that of the function.

A function declaration is also called a function specification or function spec.

Note:

This topic applies to nested functions.

For information about standalone functions, see "CREATE FUNCTION Statement".

For information about package functions, see "CREATE PACKAGE Statement".

Topics

Syntax

function_declaration ::=

Description of the illustration function_declaration.eps

function_heading ::=

Description of the illustration function_heading.eps

( datatype ::= , parameter_declaration ::= )

function_definition ::=

Description of the illustration function_definition.eps

( body ::= , declare_section ::= , pipelined_clause ::= , deterministic_clause ::= , parallel_enable_clause ::= , result_cache_clause ::= , call_spec ::= )

Semantics

function_declaration

Declares a function, but does not define it. The definition must appear later in the same block, subprogram, or package as the declaration.

function_heading

The function heading specifies the function name and its parameter list.

function_name

Name of the function that you are declaring or defining.

RETURN datatype

Specifies the data type of the value that the function returns, which can be any PL/SQL data type (see PL/SQL Data Types).

Restriction on datatype

You cannot constrain this data type (with NOT NULL, for example). If datatype is a constrained subtype, then the returned value does not inherit the constraints of the subtype (see "Formal Parameters of Constrained Subtypes").

function_definition

Either defines a function that was declared earlier or both declares and defines a function.

declare_section

Declares items that are local to the function, can be referenced in body, and cease to exist when the function completes execution.

body

Required executable part and optional exception-handling part of the function. In the executable part, at least one execution path must lead to a RETURN statement; otherwise, a runtime error occurs.

Examples

Example 8-2, "Declaring, Defining, and Invoking a Simple PL/SQL Function"