Lecture Notes Unit5 chapter18 Packages.pdf

RDBMS - Unit V
Chapter 18
Packages
Prepared By
Dr. S.Murugan, Associate Professor
Department of Computer Science,
Alagappa Government Arts College, Karaikudi.
(Affiliated by Alagappa University)
Mailid: muruganjit@gmail.com
Reference Book:
LEARN ORACLE 8i, JOSE A RAMALHO

Package - Definition
➢ A package is a collection of database objects, such as
stored procedures, functions, variables, constants, and
cursors.
➢ A package may contain subprograms that can be called
from a trigger, procedure, or function.
➢ A package also improves machine performance,
because it simultaneously transfers several objects to
the memory.

Package Structure
➢ A package has two sections: the specification section
and the body section.
➢ They need to be created separately.

Specification Section
➢ The specification section is a type of summary for the
contents of the package body
➢ The specification section is created with the CREATE
PACKAGE command, as shown below:
Syntax:
CREATE [OR REPLACE] PACKAGE [schema.]
package {IS | AS} pl/sql_package_spec
➢ Arguments
OR REPLACE
Re-creates the package specification if it already exists.

Specification Section
schema
➢ The schema that will contain the package. If schema is
omitted, Oracle creates the package in its own schema.
package
➢ The name of the package to be created.
pl/sql_package_spec
➢ The package specification. It can declare program
objects. Package specifications are written in PL/SQL.

Package Body
➢ The package body contains the formal definition of all
the objects referenced in the declaration section.
➢ The package body is created with the CREATE
PACKAGE BODY command, as shown below:
➢ Syntax:
CREATE [OR REPLACE] PACKAGE BODY [schema.]
package {IS | AS} pl/sql_package_body

Package Body
Arguments:
OR REPLACE
➢ Re-creates the body of the package if it already exists.
Schema
➢ The schema that will contain the package. If schema is
omitted, Oracle creates it in its own schema.
package
➢ The name of the package to be created.
pl/sql_package_body
➢ The body of the package. It can declare and define
program objects. Package bodies are written in
PL/SQL.

Steps to working with package
1. Create a package (Declaration of function and
procedure)
2. Compile the package
3. Create a package body (Definition of function and
procedure)
4. Compile the package body
5. Execute the procedure by using the following
command.
Exec packagename.procedurename(argument list)
Ex: Exec genemp.increase2(1001,10)
6. Execute the function by using the following command.
Select packagename.functionname(argument) from dual.
Ex: Select genemp.countemp(1001) from dual.

Package Creation
create PACKAGE GENEMP1 AS
PROCEDURE increase2 (veno IN
emp2.eno%type,percent number);
function countemp (vdno in employee.dno%type)
RETURN number;
END;
/

Package Body Creation
create package body genemp1 is
PROCEDURE increase2 (veno IN emp2.eno%type,percent
number) IS
BEGIN
update emp2 set salary=salary*(1+percent/100)
where eno=veno;
END;
function countemp (vdno in empl.dno%type)return number is
emptot number;
begin
select count(*) into emptot from empl where dno=vdno;
return emptot;
end;
end;
/

Referencing a Package Subprogram
To access the procedure specified inside a package, then
use the packagename associated with the procedure name.
SQL> Exec genemp.increase2(105,10)
PL/SQL procedure successfully completed.
To access the function specified inside a package, then
use the packagename associated with the function name.
SQL> Select genemp.countemp(101) from dual;
PL/SQL procedure successfully completed.

Deleting a Package
➢ To delete the package then use the following
command
SQL> Drop package package name
Ex: Drop package genemp;
➢ To delete the package body then use the following
command
SQL> Drop package body package name
Ex: Drop package body genemp;

Oracle Packages
➢ Oracle has dozens of packages containing procedures
that extend its functionality. Most of them start with
the prefix DBMS_, UTL_ , DEBUG_ , or OUTLN_.
➢ Following is an example of the use of the
DBMS_OUTPUT package, which is called by a
trigger that is enabled when any DML operation is
performed in the EMP2 table:

Oracle Packages
CREATE OR REPLACE TRIGGER saldif
BEFORE DELETE OR INSERT OR UPDATE ON emp2 FOR
EACH ROW WHEN (new.eno > 0)
DECLARE
sal_diff number;
BEGIN
sal_diff := :new.salary - :old.salary;
dbms_output.put(' Old: ' || :old.salary);
dbms_output.put(' New: ' || :new.salary);
dbms_output.put_line(' Difference ' || sal_diff);
END;
/
Output:
SQL> update emp2 set sal=sal*1.3 where eno=101;
Old: 1100 New: 1430 Difference 330

Lecture Notes Unit5 chapter18 Packages.pdf

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