CREATE PROCEDURE

Purpose

Use the CREATE PROCEDURE statement to create a standalone stored procedure or a call specification.

A procedure is a group of PL/SQL statements that you can call by name. A call specification (sometimes called call spec) declares a Java method or a third-generation language (3GL) routine so that it can be called from SQL and PL/SQL. The call spec tells Oracle Database which Java method to invoke when a call is made. It also tells the database what type conversions to make for the arguments and return value.

Stored procedures offer advantages in the areas of development, integrity, security, performance, and memory allocation.

Prerequisites

Before creating a procedure, the user SYS must run a SQL script commonly called DBMSSTDX.SQL. The exact name and location of this script depend on your operating system.

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

To invoke a call spec, you may need additional privileges, for example, the EXECUTE object privilege on the C library for a C call spec.

To embed a CREATE PROCEDURE statement inside an Oracle precompiler program, you must terminate the statement with the keyword END-EXEC followed by the embedded SQL statement terminator for the specific language.

Syntax

create_procedure::=

Description of the illustration create_procedure.gif

invoker_rights_clause::=

Description of the illustration invoker_rights_clause.gif

call_spec::=

Description of the illustration call_spec.gif

Java_declaration::=

Description of the illustration java_declaration.gif

C_declaration::=

Description of the illustration c_declaration.gif

Semantics

OR REPLACE

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

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

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

schema

Specify the schema to contain the procedure. If you omit schema, then the database creates the procedure in your current schema.

procedure

Specify the name of the procedure to be created.

If creating the procedure results in compilation errors, then the database returns an error. You can see the associated compiler error messages with the SQL*Plus command SHOW ERRORS.

argument

Specify the name of an argument to the procedure. If the procedure does not accept arguments, then you can omit the parentheses following the procedure name.

IN Specify IN to indicate that you must supply a value for the argument when calling the procedure.

OUT  Specify OUT to indicate that the procedure passes a value for this argument back to its calling environment after execution.

IN OUT Specify IN OUT to indicate that you must supply a value for the argument when calling the procedure and that the procedure passes a value back to its calling environment after execution.

If you omit IN, OUT, and IN OUT, then the argument defaults to IN.

NOCOPY  Specify NOCOPY to instruct the database to pass this argument as fast as possible. This clause can significantly enhance performance when passing a large value like a record, an index-by table, or a varray to an OUT or IN OUT parameter. IN parameter values are always passed NOCOPY.

• When you specify NOCOPY, assignments made to a package variable may show immediately in this parameter, or assignments made to this parameter may show immediately in a package variable, if the package variable is passed as the actual assignment corresponding to this parameter.

• Similarly, changes made either to this parameter or to another parameter may be visible immediately through both names if the same variable is passed to both.

• If the procedure is exited with an unhandled exception, then any assignment made to this parameter may be visible in the caller's variable.

These effects may or may not occur on any particular call. You should use NOCOPY only when these effects would not matter.

datatype Specify the datatype of the argument. An argument can have any datatype supported by PL/SQL.

Datatypes cannot specify length, precision, or scale. For example, VARCHAR2(10) is not valid, but VARCHAR2 is valid. Oracle Database derives the length, precision, and scale of an argument from the environment from which the procedure is called.

DEFAULT expr Use this clause to specify a default value for the argument. Oracle Database recognizes the characters := in place of the keyword DEFAULT.

invoker_rights_clause

The invoker_rights_clause lets you specify whether the procedure executes with the privileges and in the schema of the user who owns it or with the privileges and in the schema of CURRENT_USER.

This clause also determines how the database resolves external names in queries, DML operations, and dynamic SQL statements in the procedure.

AUTHID CURRENT_USER

Specify CURRENT_USER to indicate that the procedure executes with the privileges of CURRENT_USER. This clause creates an invoker-rights procedure.

This clause also specifies that external names in queries, DML operations, and dynamic SQL statements resolve in the schema of CURRENT_USER. External names in all other statements resolve in the schema in which the procedure resides.

AUTHID DEFINER

Specify DEFINER to indicate that the procedure executes with the privileges of the owner of the schema in which the procedure resides, and that external names resolve in the schema where the procedure resides. This is the default and creates a definer-rights procedure.

IS | AS Clause

Use the appropriate part of this clause to declare the procedure.

pl/sql_subprogram_body

Declare the procedure in a PL/SQL subprogram body.

call_spec

Use the call_spec to map a Java or C method name, parameter types, and return type to their SQL counterparts.

In the Java_declaration, string identifies the Java implementation of the method.

AS EXTERNAL  The AS EXTERNAL clause is an alternative way of declaring a C method. In most cases, Oracle recommends that you use the AS LANGUAGE C syntax. However, AS EXTERNAL is required if a default argument is used as one of the parameters or if one of the parameters uses a PL/SQL datatype that needs to be mapped (for example, Boolean). AS EXTERNAL causes the PL/SQL layer to be loaded so that the parameters can be properly evaluated.

Examples

Creating a Procedure: Example The following statement creates the procedure remove_emp in the schema hr. The PL/SQL is shown in italics:

CREATE PROCEDURE remove_emp (employee_id NUMBER) AS
   tot_emps NUMBER;
   BEGIN
      DELETE FROM employees
      WHERE employees.employee_id = remove_emp.employee_id;
   tot_emps := tot_emps - 1;
   END;
/

The remove_emp procedure removes a specified employee. When you call the procedure, you must specify the employee_id of the employee to be removed.

The procedure uses a DELETE statement to remove from the employees table the row of employee_id.

In the following example, external procedure c_find_root expects a pointer as a parameter. Procedure find_root passes the parameter by reference using the BY REFERENCE phrase. The PL/SQL is shown in italics:

CREATE PROCEDURE find_root
   ( x IN REAL ) 
   IS LANGUAGE C
      NAME c_find_root
      LIBRARY c_utils
      PARAMETERS ( x BY REFERENCE );