CREATE FUNCTION

Purpose

Functions are defined using PL/SQL. Therefore, this section provides some general information but refers to Oracle Database PL/SQL Language Reference for details of syntax and semantics.

Use the CREATE FUNCTION statement to create a standalone stored function or a call specification.

• A stored function (also called a user function or user-defined function) is a set of PL/SQL statements you can call by name. Stored functions are very similar to procedures, except that a function returns a value to the environment in which it is called. User functions can be used as part of a SQL expression.

• A call specification declares a Java method or a third-generation language (3GL) routine so that it can be called from PL/SQL. You can also use the CALL SQL statement to call such a method or routine. The call specification tells Oracle Database which Java method, or which named function in which shared library, to invoke when a call is made. It also tells the database what type conversions to make for the arguments and return value. Note: You can also create a function as part of a package using the CREATE PACKAGE statement.

See Also:

• CREATE PROCEDURE for a general discussion of procedures and functions, CREATE PACKAGE for information on creating packages, ALTER FUNCTION and DROP FUNCTION for information on modifying and dropping a function

• CREATE LIBRARY for information on shared libraries

• Oracle Database Development Guide for more information about registering external functions

Prerequisites

To create or replace a function in your own schema, you must have the CREATE PROCEDURE system privilege. To create or replace a function in another user’s schema, you must have the CREATE ANY PROCEDURE system privilege.

Syntax

Functions are defined using PL/SQL. Therefore, the syntax diagram in this book shows only the SQL keywords. Refer to Oracle Database PL/SQL Language Reference for the PL/SQL syntax, semantics, and examples.

create_function::=

Description of the illustration create_function.eps

(plsql_function_source: See Oracle Database PL/SQL Language Reference.)

Semantics

OR REPLACE

Specify OR REPLACE to re-create the function if it already exists. Use this clause to change the definition of an existing function without dropping, re-creating, and regranting object privileges previously granted on the function. If you redefine a function, then Oracle Database recompiles it.

Users who had previously been granted privileges on a redefined function can still access the function without being regranted the privileges.

If any function-based indexes depend on the function, then Oracle Database marks the indexes DISABLED.

See Also: ALTER FUNCTION for information on recompiling functions using SQL

[ EDITIONABLE | NONEDITIONABLE ]

Use these clauses to specify whether the function is an editioned or noneditioned object if editioning is enabled for the schema object type FUNCTION in schema. The default is EDITIONABLE. For information about editioned and noneditioned objects, see Oracle Database Development Guide.

IF NOT EXISTS

Specifying IF NOT EXISTS has the following effects:

• If the function does not exist, a new one is created at the end of the statement.

• If the function exists, it is detected and a new one is not created.

You can only specify OR REPLACE or IF NOT EXISTS in a statement at a time. Using both OR REPLACE with IF NOT EXISTS in the very same statement results in an error.

You cannot specify IF EXISTS with CREATE statements.

Note: You can use IF [NOT] EXISTS only from Release 19.28 and up.

plsql_function_source

See Oracle Database PL/SQL Language Reference for the syntax and semantics of the plsql_function_source, including examples.