A package is a schema object that groups logically related PL/SQL types, items, and subprograms. Use packages when writing a set of related subprograms that form an application programming interface (API) that you or others might reuse. Packages have two parts: a specification (spec for short) and a body. For more information, see Chapter 9, "Using PL/SQL Packages". For an example of a package declaration, see Example 9-3.
This section discusses the package specification and body options for PL/SQL. For information on the
PACKAGE SQL statement, see Oracle Database SQL Reference. For information on the
BODY SQL statement, see Oracle Database SQL Reference.
package specification ::=
package body ::=
Publishes a Java method or external C function in the Oracle data dictionary. It publishes the routine by mapping its name, parameter types, and return type to their SQL counterparts. For more information, see Oracle Database Java Developer's Guide and Oracle Database Application Developer's Guide - Fundamentals.
Declares a collection (nested table, index-by table, or varray). For the syntax of
collection_declaration, see "Collection Definition".
Defines a collection type using the datatype specifier
Declares a constant. For the syntax of
constant_declaration, see "Constant and Variable Declaration".
Defines the underlying implementation of an explicit cursor. For the syntax of
cursor_body, see "Cursor Declaration".
Declares the interface to an explicit cursor. For the syntax of
cursor_spec, see "Cursor Declaration".
Declares an exception. For the syntax of
exception_declaration, see "Exception Definition".
Implements a function. For the syntax of
function_body, see "Function Declaration".
Declares the interface to a function. For the syntax of
function_spec, see "Function Declaration".
Declares an object (instance of an object type). For the syntax of
object_declaration, see "Object Type Declaration".
A package stored in the database. For naming conventions, see "Identifiers".
RESTRICT_REFERENCES, which checks for violations of purity rules. To be callable from SQL statements, a function must obey rules that control side effects. If any SQL statement inside the function body violates a rule, you get an error at run time (when the statement is parsed). For the syntax of the pragma, see "RESTRICT_REFERENCES Pragma".
The pragma asserts that a function does not read and/or write database tables and/or package variables. For more information about the purity rules and pragma
RESTRICT_REFERENCES, see Oracle Database Application Developer's Guide - Fundamentals.
Marks a package as serially reusable, if its state is needed only for the duration of one call to the server (for example, an OCI call to the server or a server-to-server remote procedure call). For more information, see Oracle Database Application Developer's Guide - Fundamentals.
Implements a procedure. For the syntax of
procedure_body, see "Procedure Declaration".
Declares the interface to a procedure. For the syntax of
procedure_spec, see "Procedure Declaration".
Declares a user-defined record. For the syntax of
record_declaration, see "Record Definition".
Defines a record type using the datatype specifier
RECORD or the attribute
The schema containing the package. If you omit
schema_name, Oracle assumes the package is in your schema.
Declares a variable. For the syntax of
variable_declaration, see "Constant and Variable Declaration".
You can use any Oracle tool that supports PL/SQL to create and store packages in an Oracle database. You can issue the
BODY statements interactively from SQL*Plus, or from an Oracle Precompiler or OCI host program. However, you cannot define packages in a PL/SQL block or subprogram.
Most packages have a specification and a body. The specification is the interface to your applications; it declares the types, variables, constants, exceptions, cursors, and subprograms available for use. The body fully defines cursors and subprograms, and so implements the spec.
Only subprograms and cursors have an underlying implementation. If a specification declares only types, constants, variables, exceptions, and call specifications, the package body is unnecessary. The body can still be used to initialize items declared in the specification:
CREATE OR REPLACE PACKAGE emp_actions AS -- additional code here ... number_hired INTEGER; END emp_actions; / CREATE OR REPLACE PACKAGE BODY emp_actions AS BEGIN number_hired := 0; END emp_actions; /
You can code and compile a spec without its body. Once the spec has been compiled, stored subprograms that reference the package can be compiled as well. You do not need to define the package bodies fully until you are ready to complete the application. You can debug, enhance, or replace a package body without changing the package spec, which saves you from recompiling subprograms that call the package.
Cursors and subprograms declared in a package spec must be defined in the package body. Other program items declared in the package spec cannot be redeclared in the package body.
To match subprogram specs and bodies, PL/SQL does a token-by-token comparison of their headers. Except for white space, the headers must match word for word. Otherwise, PL/SQL raises an exception.
Variables declared in a package keep their values throughout a session, so you can set the value of a package variable in one procedure, and retrieve the same value in a different procedure.
For examples, see the following: