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Packages

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Packages - Objectives

At the end of this session, the participants will be able to:

Understand the need for Packages

Write a Package specification

Write a Package body

Overloading subprograms

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Packages

A Package is a PL/SQL construct that allows related objects to be storedtogether

A Package is a stored database object

Groups together procedures, functions, cursor, types and variables

Other PL/SQL blocks can reference packages

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Packages (contd)

Package has two components:

Package SpecificationPackage body

Package Specification:

- Declares types, variables, constants, exceptions, cursors and subprogramsavailable for use.

- Constructs declared in the package specifications are public.

Syntax:

CREATE OR REPLACE PACKAGE package_name IS

procedure_specification

function_specification

variable_declarationcursor_declaration etc.

END package_name;

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Packages (contd)

Package Body:

- It defines cursors and subprograms and soimplements the specification

- It can not be successfully compiled unless thepackage header has already been successfully

compiled

Syntax:

CREATE OR REPLACE PACKAGE BODY package_name IS

private_variable

procedure_definition

function_definition etc.

private function or procedure definition

END package_name;

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Packages

A package body contains the blocks and specifications for all of the publicobjects listed in the package specification.

The package body may include objects that are not listed in the packagespecification.

Such object are said to be private and are not available to users of thepackage.

Private objects may only be called by other objects within the samepackage body.

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Packages - Advantages

Advantages of Packages

1. Modularity:encapsulates logically relatedprogramming structures in a named module

2. Easier Application Design:Initially only theinterface information in the package specification isrequired

3. Information hiding:Constructs can be public orprivate

4. Better Performance:When a packagedsubprogram is called the first time, the entirepackage is loaded into memory

5. Overloading:Packages allow you to overloadprocedures and functions

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Packages: Example

Creating a Package Specification

CREATE OR REPLACE PACKAGE emp_pack

IS

PROCEDURE emp_add(p_empno IN emp.empno%TYPE,

p_ename IN emp.ename%TYPE,p_esal IN emp.sal%TYPE,

p_deptno IN emp.deptno%TYPE);

PROCEDURE emp_del (p_empno IN emp.empno%TYPE);

END emp_pack;

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Packages: Example (contd)

Creating a Package Body

CREATE OR REPLACE PACKAGE BODY emp_packIS

FUNCTION valid_deptno(p_deptno dept.deptno%TYPE)

RETURN BOOLEAN

IS

dummy NUMBER;BEGIN

SELECT deptno into dummy FROM dept

WHERE deptno=p_deptno;

RETURN TRUE;

EXCEPTION

WHEN NO_DATA_FOUND THEN

RETURN FALSE;

END;

Contd

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Packages: Example (contd)

PROCEDURE emp_add(p_empno IN emp.empno%TYPE,

p_ename IN emp.ename%TYPE,

p_esal IN emp.sal%TYPE,p_deptno IN emp.deptno%TYPE)

IS

BEGIN

IF valid_deptno(p_deptno) THEN

INSERT INTO emp(empno,ename,sal,deptno)VALUES(p_empno,p_ename,p_esal,p_deptno);

DBMS_OUTPUT.PUT_LINE('Emp# : '||p_empno||' added totable');

COMMIT;

ELSERAISE_APPLICATION_ERROR(-20010,Invalid

departmentTry again);

END IF

END;

Contd

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Packages: Example (contd)

PROCEDURE emp_del(p_empno IN emp.empno%TYPE)

ISBEGIN

DELETE FROM emp

WHERE empno=p_empno;

IF SQL%NOTFOUND THEN

RAISE_APPLICATION_ERROR(-20120,Employee Not Deleted);

ELSE DBMS_OUTPUT.PUT_LINE(SQL%ROWCOUNT||' ROWSDELETED'); END IF;

END emp_del;

END emp_pack;

Invoking a packaged procedure or function from SQL*Plus

EXECUTE emp_pack.emp_del(1001)

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Packages: Forward Declarations

Identifiers must be declared before referencing them

CREATE OR REPLACE PACKAGE BODY forward_pack

IS

PROCEDURE award_bonus (. . .)

IS

BEGIN

calc_rating(. . .);--illegal referenceEND;

FUNCTION calc_rating ( . . . )

RETURN NUMBER

IS

BEGINRETURN ;

END;

END forward_pack;

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Packages: Forward Declarations (contd)

CREATE OR REPLACE PACKAGE BODY forward_pack

IS-- Forward declaration

FUNCTION calc_rating(. . .) RETURN NUMBER;

PROCEDURE award_bonus (. . .)

IS

BEGIN

calc_rating(. . .);-- Legal referenceEND;

FUNCTION calc_rating ( . . . )

RETURN NUMBER

IS

BEGIN

RETURN ;

END;

END forward_pack;

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Packages

When creating packages, the package specification and the packagebody are created separately. Thus, there are two commands to use:create package for the package specification, and create package bodyfor the package body.

Both of these commands require that you have the

CREATE PROCEDURE system privilege.

If the package is to be created in a schema other than your own, then youmust have the

CREATE ANY PROCEDURE system privilege.

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Dropping Package

Dropping package specification:

DROP PACKAGE package_name;

Dropping package body:

DROP PACKAGE BODY package_name;

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Exercise

CREATE OR REPLACE PACKAGE BB_PACK

IS

V_MAX_TEAM_SALARY NUMBER(12,2);

PROCEDURE ADD_PLAYER(V_ID IN NUMBER, V_LAST_NAME

VARCHAR2, V_SALARY NUMBER);

END BB_PACK;

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Exercise (Cont..)

CREATE OR REPLACE PACKAGE BODY BB_PACK

IS

PROCEDURE UPD_PLAYER_STAT

(V_ID IN NUMBER, V_AB IN NUMBER DEFAULT 4, V_HITS IN NUMBER)

IS

BEGINUPDATE PLAYER_BAT_STAT SET AT_BATS = AT_BATS + V_AB,

HITS = HITS + V_HITS WHERE PLAYER_ID = V_ID;

COMMIT;

END UPD_PLAYER_STAT;

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Exercise (Cont..)

PROCEDURE ADD_PLAYER

(V_ID IN NUMBER, V_LAST_NAME VARCHAR2, V_SALARY NUMBER)

IS

BEGIN

INSERT INTO PLAYER(ID,LAST_NAME,SALARY)

VALUES (V_ID, V_LAST_NAME, V_SALARY);UPD_PLAYER_STAT(V_ID,0,0);

END ADD_PLAYER;

END BB_PACK;

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Exercise (Cont..)

You make a change to the body of the BB_PACK package. The BB_PACKbody is recompiled.

What happens if the stand alone procedure VALIDATE_PLAYER_STATreferences this package?

A. VALIDATE_PLAYER_STAT cannot recompile and must be recreated.

B. VALIDATE_PLAYER_STAT is not invalidated.

C. VALDIATE_PLAYER_STAT is invalidated.

D. VALIDATE_PLAYER_STAT and BB_PACK are invalidated.

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Summary

We have discussed:

Parts of a Package

Coding a procedure/function within a Package

Overloading Subprograms within a Package

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Questions

Thank You