Advanced Databases Advanced PL/SQL Programming: Procedure, Function and Package.

Advanced Databases

Advanced PL/SQL Programming:Procedure, Function and Package

Anonymous PL/SQL Programs

• Write code in text editor, execute it in SQL*Plus

• Code can be stored as text in file system• Program cannot be called by other

programs, or executed by other users• Cannot accept or pass parameter values

Named PL/SQL Programs

• Can be created:– Using text editor & executed in SQL*Plus– Using Procedure Builder

• Can be stored:– As compiled objects in database– As source code libraries in file system

• Can be called by other programs• Can be executed by other users

Named Program Locations

• Server-side– Stored in database as database objects– Execute on the database server

• Client-side– Stored in the client workstation file system– Execute on the client workstation

Named Program Types

• Program Units (client or server-side)– Procedures– Functions

• Libraries (client-side)

• Packages (client or server-side)

• Triggers (server-side)

Program Units

• Procedures– Can receive and pass multiple parameter

values– Can call other program units

• Functions– Like procedures, except they return a single

value

Variables used to pass data values in/out of program units

Declared in the procedure header Parameter values are passed when the

procedure is called from the calling program

Parameters

Parameter Modes

• IN– Incoming values, read-only (default)

• OUT– Outgoing values, write-only

• IN OUT– Can be both incoming and outgoing

Creating a Procedure

CREATE OR REPLACE PROCEDURE procedure_name

(parameter1 mode datatype,

parameter2 mode datatype, …

) IS | AS

local variable declarations

BEGIN

program statements

EXCEPTION

exception handlers

END;

header

body

Executing a Procedure

EXECUTE procedure_name

(parameter1_value, parameter2_value, …);

Formal parameters: declared in procedure header

Actual parameters: values placed in parameter list when procedure is called

Values correspond based on order

Procedure Header:PROCEDURE calc_gpa (s_id IN NUMBER, term_id IN NUMBER, gpa OUT NUMBER);

Procedure Call:calc_gpa (current_s_id, 4, current_gpa);

Parameter Types

Formal Parameters

Actual Parameters

Dropping A Procedure

• DROP PROCEDURE proc_name

Creating a Function

CREATE OR REPLACE FUNCTION function_name (parameter1 mode datatype,

parameter2 mode datatype, … ) RETURN function_return_data_typeIS local variable declarationsBEGIN program statements RETURN return_value;EXCEPTION exception handlers

RETURN EXCEPTION_NOTICE;END;

header

body

Function Syntax Details

• RETURN command in header specifies data type of value the function will return

• RETURN command in body specifies actual value returned by function

Calling a Function

• Can be called from either named or anonymous PL/SQL blocks

• Can be called within SQL queries

return_value :=

function_name(parameter1_value, parameter2_value, …);

Stored Program UnitObject Privileges

• Stored program units exist as objects in your database schema

• To allow other users to use your units, you must grant them EXECUTE privileges

GRANT EXECUTE ON unit_name TO username;

Using Stored Program UnitsThat Belong to Other Users

• You must have been granted the privilege to use it

• You must preface the unit name with the owner’s username

return_value

:= LHOWARD.my_function

TO_DATE(’07/14/1958’, ‘MM/DD/YYYY’);

Calling Procedures From Other Procedures

• Use procedure name followed by parameter list

procedure_name

(parameter1_value, parameter2_value, …);

Create or replace PROCEDURE Get_emp_names (Dept_num IN NUMBER) IS Emp_name VARCHAR2(30);

CURSOR c1 (Depno NUMBER) IS SELECT Empname FROM Emp WHERE deptno = Depno;BEGIN OPEN c1(Dept_num); LOOP FETCH c1 INTO Emp_name; EXIT WHEN C1%NOTFOUND; DBMS_OUTPUT.PUT_LINE(Emp_name); END LOOP; CLOSE c1;

END;

Example// Procedure that prints all employees for a given department number

Example// Function that returns the monthly salary for an employee

CREATE OR REPLACE FUNCTION MYFUNC1 (emp_no integer)RETURN NUMBERIS

Monthly_sal NUMBER(10,2);BEGIN SELECT round (annsalary/12) INTO Monthly_sal FROM Emp WHERE empno = emp_no;RETURN (Monthly_sal);

END MYFUNC1;/

Packages

• Server-side code library

• Can contain:– Global variable declarations– Cursors– Procedures– Functions

Package Components

• Specification– Used to declare all public variables, cursors,

procedures, functions

• Body– Contains underlying code for procedures and

functions

• Rationale:– Specification is visible to users, gives details on how

to use– Body is not visible, users don’t care about details

Creating a Package Specification in SQL*Plus

CREATE OR REPLACE PACKAGE package_name IS --public variables variable_name datatype;

--program units PROCEDURE procedure_name (parameter_list); FUNCTION function_name (parameter_list);END;

Creating a Package Specification in SQL*Plus

Creating a Package Body in SQL*Plus

CREATE OR REPLACE PACKAGE BODY package_name IS private variable declarations program unit blocksEND;

Creating a Package Body in SQL*Plus

Calling a Program Unit That Is In a Package

• Preface the program unit name with the package name

PACKAGE_NAME.program_unit_name(parameter_list);

• Example:

DBMS_OUTPUT.PUT_LINE(‘Hello World’);

Overloading Program Units in Packages

• Overloading– Multiple program units have the same name,

but accept different input parameters

• Allows user to use the same command to perform an action but pass different parameter values

Package Specification With Overloaded Procedures