PL/SQL TUTORIAL

WHAT IS PL/SQL

pl/sql is the procedural implementation of sql i.e. u can pass sql statements in procedural format using pl/sql. Normal sql does not have any procedural capabilities moreover u can only pass one statement at a time to Oracle Engine. Hence, pl/sql have come up to avoid this limitation. Hence, pl/sql is the structured programming language for oracle. It’s structure is very much similar to any other procedural language such as C or C++

I won’t waste your time in typing out the advantages of pl/sql … u can easily find out in a book.

PL/SQL BLOCK

The pl/sql block contains the following section:–

—–The DECLARE section.
—–The Master BEGIN and END section that contains the EXCEPTION section.

The declare section contains declaration of memory variables, constants, cursors etc. The begin section contains sql executable statements and pl/sql executable statements. The exception section contains code to handle errors that may arise during the execution of the code block. The end declares the end of pl/sql block.

A bit about it’s working. When you typed out the pl/sql block for execution. It is sent to the pl/sql engine, whee procedural statements are executed; and sql statements are sent to the sql executor in the oracle engine. Since pl/sql engine resides in the oracle engine, the codes executes smoothly and efficiently.

PL/SQL DATA-TYPE

This is easy since it includes almost all the data types which u have used in sql such as date, varchar, number, char etc etc… Some of the attributes such as %TYPE is also used. This attribute automatically takes in the default datatype of the sql table from which u have passed the query. We will discuss this later.

Remember in pl/sql a variable name must begin with a character and can be followed by maximum of 29 other characters. Reserved words can’t be used unless enclosed within double quotes. Variables must be seperated from each other by at least one space or by a punctuation mark. You can assign values of operator using := operator. I won’t discuss about logical comparisons operators such as <, > , >=, NOT, TRUE, AND, OR, NULL etc since they r quite easy to understand.

MOST IMPORTANT: HOW TO DISPLAY MESSAGES ON SCREEN —
DBMS_OUTPUT : is a package that includes a number of procedure and functions that accumulate information in a buffer so that it can be retrieved later. These functions can also be used to display messages to the user.
PUT_LINE : Put a piece of information in the package buffer followed by an end-of-line marker. It can also be used to display message to the user. Put_line expects a single parameter of character data type. If used to display a message, it is the message ’string’.
EG: dbms_output.put_line(x);

REMEMBER: To display messages to the user the SERVEROUTPUT should be set to ON. SERVEROUTPUT is a sql*plus environment parameter that displays the information pased as a parameter to the PUT_LINE function.
EG: SET SERVEROUTPUT ON

A bit about comments. A comment can have 2 forms i.e.
– The comment line begins with a double hyphen (–). The entire line will be treated as a comment.
– The C style comment such as /* i am a comment */

CONDITIONAL CONTROL AND ITERATIVE CONTROL AND SEQUENTIAL CONTROL

IF and else…..
IF –Condition THEN
–Action
ELSEIF –Condition THEN
–Action
ELSE
–Action
END IF;

SIMPLE LOOP
loop
– Sequence of statements;
end loop;

the loop ends when u use EXIT WHEN statement –condition

WHILE LOOP
While –condition
loop
–sequence of statements
end loop;

FOR LOOP
FOR i in 1..10
loop
–sequence of statements
end loop;

GOTO (sequential control)
GOTO X;
<< X >>

EXAMPLES

--ADDITION
declare
         a number;
         b number;
         c number;
begin
         a:=&a;
         b:=&b;
         c:=a+b;
         dbms_output.put_line('Sum of ' || a || ' and ' || b || ' is ' || c);

Here & is used to take user input at runtime.....

--SUM OF 100 NUMBERS

Declare
	a number;
	s1 number default 0;
Begin
	a:=1;
	loop
		s1:=s1+a;
		exit when (a=100);
		a:=a+1;
	end loop;
	dbms_output.put_line('Sum between 1 to 100 is '||s1);
End;

--SUM OF odd NUIMBERS USING USER INPUT...for loop
declare
        n number;
        sum1 number default 0;
        endvalue number;
begin
        endvalue:=&endvalue;
        n:=1;
        for n in 1.. endvalue
        loop
             if mod(n,2)=1
             then
                  sum1:=sum1+n;
             end if
        end loop;
        dbms_output.put_line('sum = ' || sum1);
end;

--SUM OF 100 ODD NUMBER .. WHILE LOOP
declare
        n number;
        endvalue number;
        sum1 number default 0;
begin
        endvalue:=&endvalue;
        n:=1;
        while (n < endvalue)
        loop
             sum1:=sum1+n;
             n:=n+2;
        end loop;
        dbms_output.put_line('Sum of odd numbers between 1 and ' || endvalue || ' is ' || sum1);
end;

--CALCULATION OF NET SALARY
declare
        ename varchar2(15);
        basic number;
        da number;
        hra number;
        pf number;
        netsalary number;
begin
        ename:=&ename;
        basic:=&basic;

        da:=basic * (41/100);
        hra:=basic * (15/100);

        if (basic < 3000)
        then
             pf:=basic * (5/100);
        elsif (basic >= 3000 and basic <= 5000)
        then
             pf:=basic * (7/100);
        elsif (basic >= 5000 and basic <= 8000)
        then
             pf:=basic * (8/100);
        else
             pf:=basic * (10/100);
        end if;
        netsalary:=basic + da + hra -pf;
        dbms_output.put_line('Employee name : ' || ename);
        dbms_output.put_line('Providend Fund : ' || pf);
        dbms_output.put_line('Net salary : ' || netsalary);
end;

--MAXIMUM OF 3 NUMBERS
Declare
	a number;
	b number;
	c number;
	d number;
Begin
	dbms_output.put_line('Enter a:');
	a:=&a;
	dbms_output.put_line('Enter b:');
	b:=&b;
	dbms_output.put_line('Enter c:');
	c:=&b;
	if (a>b) and (a>c) then
		dbms_output.putline('A is Maximum');
	elsif (b>a) and (b>c) then
		dbms_output.putline('B is Maximum');
	else
		dbms_output.putline('C is Maximum');
	end if;
End;

--QUERY EXAMPLE--IS SMITH EARNING ENOUGH
declare
        s1 emp.sal %type;
begin
        select sal into s1 from emp
        where ename = 'SMITH';
        if(no_data_found)
        then
           raise_application_error
           (20001,'smith is not present');
        end if;

        if(s1 > 10000)
        then
           raise_application_error
           (20002,'smith is earning enough');
        end if;

        update emp set sal=sal + 500
        where ename='SMITH';
end;

--PRIME NO OR NOT
DECLARE
	no NUMBER (3) := &no;
	a NUMBER (4);
	b NUMBER (2);
BEGIN
	FOR i IN 2..no - 1
	LOOP
		a := no MOD i;
		IF a = 0
		THEN
			GOTO out;
		END IF;
	END LOOP;
	<>
	IF a = 1
	THEN
		DBMS_OUTPUT.PUT_LINE (no || ' is a prime number');
	ELSE
		DBMS_OUTPUT.PUT_LINE (no || ' is not a prime number');
	END IF;
END;

--SIMPLE EXAMPLE OF LOOP STATEMENT I.E. EXIT WHEN
Declare
a number:= 100;
begin
loop
a := a+25;
exit when a=250;
end loop;
dbms_output.put_line (to_Char(a));
end;

--EXAMPLE OF WHILE LOOP
Declare
i number:=0;
j number:= 0;
begin
while i <=100 loop
j := j+1;
i := i +2;
end loop;
dbms_output.put_line(to_char(i));
end;

--EXAMPLE OF FOR LOOP
Declare
begin
for i in 1..10
loop
dbms_output.put_line(to_char(i));
end loop;
end;

--SEQUENTIAL CONTROL GOTO.....
declare
--takes the default datatype of the column of the table price
cost price.minprice%type;
begin
select stdprice into cost from price where prodial in (Select prodid from product where prodese = "shampoo");
if cost > 7000 then
goto Upd;
end if;
<< Upd >>
Update price set minprice = 6999 where prodid=111;
end;

--CALCULATE THE AREA OF A CIRCLE FOR A VALUE OF RADIUS VARYING FROM 3 TO 7. STORE THE RADIUS AND THE CORRESPONDING VALUES OF CALCULATED AREA IN A TABLE AREAS.

Declare
pi constant number(4,2) := 3.14;
radius number(5);
area number(14,2);

Begin
radius := 3;
While radius <=7
Loop
area := pi* power(radius,2);
Insert into areas values (radius, area);
radius:= radius+1;
end loop;
end;

--INVERTING A NUMBER 5639 TO 9365
Declare
given_number varchar(5) := '5639';
str_length number(2);
inverted_number varchar(5);

Begin
str_length := length(given_number);
For cntr in reverse 1..str_length
loop
inverted_number := inverted_number || substr(given_number, cntr, 1);
end loop;
dbms_output.put_line('The Given no is ' || given_number);
dbms_output.put_line('The inverted number is ' || inverted_number);
end;

EXCEPTION HANDLING

Errors in pl/sql block can be handled...error handling refers to the way we handle the errors in pl/sql block so that no
crashing stuff of code takes place...This is exactly the same as we do in C++ or java..right!!
There are two type:
===> predefined exceptions
===> user defined exceptions
The above 2 terms are self explanatory

predefined exceptions:

No-data-found            ==   when no rows are returned
Cursor-already-open ==   when a cursor is opened in advance
Dup-val-On-index      ==   for duplicate entry of index..
Storage-error             ==   if memory is damaged
Program-error            ==   internal problem in pl/sql
Zero-divide                 ==   divide by zero
invalid-cursor             ==   if a cursor is not open and u r trying to close it
Login-denied              ==   invalid user name or password
Invalid-number          ==   if u r inserting a string datatype for a number datatype which is already declared
Too-many-rows         ==   if more rows r returned by select statement

SYNTAX


begin
sequence of statements;
exception
when --exception name then
sequence of statements;
end;

EXAMPLES

--When there is no data returned by row
declare
price item.actualprice%type;
begin
Select actual price into price from item where qty=888;
when no-data-found then
dbms_output.put_line('item missing');
end;

--EXAMPLE OF USER DEFINED EXCEPTION
DECLARE
 e_rec emp%ROWTYPE;
 e1 EXCEPTION;
 sal1 emp.sal%TYPE;
BEGIN
 SELECT sal INTO sal1 FROM emp WHERE deptno = 30 AND ename = 'John';
 IF sal1 < 5000 THEN
  RAISE e1;
  sal1 := 8500;
  UPDATE emp SET sal = sal1 WHERE deptno = 30 AND ename = 'John';
 END IF;
 EXCEPTION
  WHEN no_data_found THEN
   RAISE_APPLICATION_ERROR (-20001, 'John is not there.');
  WHEN e1 THEN
   RAISE_APPLICATION_ERROR (-20002, 'Less Salary.');
END;

--EXAMPLE OF RAISE-APPLICATION-ERROR... THIS IS YOUR OWN ERROR STATEMENT...U RAISE
--YOUR OWN ERROR

Declare
s1 emp.sal %type;
begin
select sal into s1 from emp where ename='SOMDUTT';
if(no-data-found) then
raise_application_error(20001, 'somdutt is not there');
end if;
if(s1 > 10000) then
raise_application_error(20002, 'somdutt is earing a lot');
end if;
update emp set sal=sal+500 where ename='SOMDUTT';
end;

--INTERESTING EG OF USER DEFINED EXCEPTIONS
Declare
zero-price exception;
price number(8);
begin
select actualprice into price from item where ordid =400;
if price=0 or price is null then
raise zero-price;
end if;
exception
when zero-price then
dbms_output.put_line('raised xero-price exception');
end;

CURSORS

Cursor is a work area in pl/sql which is used by sql server used to store the result of a query. Each column value is pointed using pointer. You can independently manipulate cursor values. A bit about it’s working….. suppose u ask for a query stored in the server … at first a cursor consisting of query result is created in server…now the cursor is transferred to the client where again cursor is created and hence the result is displayed……

Cursors are of 2 types: implicit and explicit…….implicit cursors are created by oracle engine itself while explicit cursors are created by the users……cursors are generally used in such a case when a query returns more than one rows….normal pl/sql returning more than one rows givens error but using cursor this limitation can be avoided….so cursors are used….

cursor attributes

%ISOPEN   == returns true if ursor is open, false otherwise
%FOUND   == returns true if recod was fetched successfully, false otherwise
%NOTFOUND  == returns true if record was not fetched successfully, false otherwise
%ROWCOUNT == returns number of records processed from the cursor.

Very important: Cursor can be controlled using following 3 control statements. They are Open, Fetch, Close…..open statement identifies the active set…i.e. query returned by select statement…close statement closes the cursor…and fetch statement fetches rows into the variables…Cursors can be made into use using cursor for loop and fetch statement…we will see the corresponding examples…

EXAMPLES

--EXAMPLE OF SQL%FOUND (IMPLICIT CURSORS)
begin
update employee set salary=salary *0.15
where emp_code = &emp_code;
if sql%found then
dbms_output.put_line('employee record modified successfully');
else
dbms_output.put_line('employee no does not exist');
end if;
end;

--EXAMPLE FOR SQL%NOTFOUND (IMPLICIT CURSORS)
begin
update employee set salary = salary*0.15 where emp_code = &emp_code;
if sql%notfound then
dbms_output.put_line('employee no . does not exist');
else
dbms_output.put_line('employee record modified successfully');
end if;
end;

--EXAMPLE FOR SQL%ROWCOUNT (IMPLICIT CURSORS)
declare
rows_affected char(4);
begin
update employee set salary = salary*0.15 where job='programmers';
rows_affected := to_char(sql%rowcount);
if sql%rowcount > 0 then
dbms_output.put_line(rows_affected || 'employee records modified successfully');
else
dbms_output.put_line('There are no employees working as programmers');
end if;
end;

Syntax of explicit cursor: Cursor cursorname is sql select statement;
Syntax of fetch : fetch cursorname into variable1, variable2…;
Syntax of close; close cursorname;
Syntax of open cursor; open cursorname;

--EXPLICIT CURSOR EG
DECLARE
	CURSOR c1 is SELECT * FROM emp;
	str_empno emp.empno%type;
	str_ename emp.ename%type;
	str_job emp.job%type;
	str_mgr emp.mgr%type;
	str_hiredate emp.hiredate%type;
	str_sal emp.sal%type;
	str_comm emp.comm%type;
	str_deptno emp.deptno%type;
	rno number;
BEGIN
	rno := &rno;
	FOR e_rec IN c1
	LOOP
		IF c1%rowcount = rno THEN
			DBMS_OUTPUT.PUT_LINE (str_empno || ' ' || str_ename || ' ' || str_job || ' ' || str_mgr || ' ' || str_hiredate || ' ' || str_sal || ' ' || str_comm || ' ' || str_deptno);
		END IF;
	END LOOP;
END;

--ANOTHER EG DISPLAYING VALUE OF A TABLE
DECLARE
	CURSOR c1 IS SELECT  * FROM emp;
	e_rec emp%rowtype;
BEGIN
	OPEN c1;
	LOOP
		FETCH c1 INTO e_rec;
		DBMS_OUTPUT.PUT_LINE('Number: ' || ' ' || e_rec.empno);
		DBMS_OUTPUT.PUT_LINE('Name  : ' || ' ' || e_rec.ename);
		DBMS_OUTPUT.PUT_LINE('Salary: ' || ' ' || e_rec.sal);
		EXIT WHEN c1%NOTFOUND;
	END LOOP;
	CLOSE c1;
END;

-- Display details of Highest 10 salary paid employee

DECLARE
	CURSOR c1 IS SELECT  * FROM emp ORDER BY sal DESC;
	e_rec emp%rowtype;
BEGIN
	FOR e_rec IN c1
	LOOP
		DBMS_OUTPUT.PUT_LINE('Number: ' || ' ' || e_rec.empno);
		DBMS_OUTPUT.PUT_LINE('Name  : ' || ' ' || e_rec.ename);
		DBMS_OUTPUT.PUT_LINE('Salary: ' || ' ' || e_rec.sal);
		EXIT WHEN c1%ROWCOUNT >= 10;
	END LOOP;
END;

-- EXAMPLE OF CURSOR FOR LOOP
declare cursor c1 is select * from somdutt;
begin
for outvariable in c1
loop
exit when c1%notfound;
if outvariable.age < 21 then
dbms_output.put_line(outvariable.age || ' ' || outvariable.name);
end if;
end loop;
end;

--ref STRONG CURSORS
DECLARE
	TYPE ecursor IS REF CURSOR RETURN emp%ROWTYPE;
	ecur ecursor;
	e_rec emp%ROWTYPE;
	dn NUMBER;
BEGIN
	dn := &deptno;
	OPEN ecur FOR SELECT * FROM emp WHERE deptno = dn;
	FOR e_rec IN ecur
	LOOP
		DBMS_OUTPUT.PUT_LINE ('Employee No    : ' || e_rec.empno);
		DBMS_OUTPUT.PUT_LINE ('Employee Salary: ' || e_rec.salary);
	END LOOP;
END;

--REF WEAK CURSORS
DECLARE
	TYPE tcursor IS REF CURSOR;
	tcur tcursor;
	e1 emp%ROWTYPE;
	d1 dept%ROWTYPE;
	tname VARCHAR2(20);
BEGIN
	tname := &tablename;
	IF tname = 'emp' THEN
		OPEN tcur FOR SELECT * FORM emp;
		DBMS_OUTPUT.PUT_LINE ('Emp table opened.');
		close tcur;
		DBMS_OUTPUT.PUT_LINE ('Emp table closed.');
	ELSE IF tname = 'dept' THEN
		OPEN tcur FOR SELECT * FROM dept;
		DBMS_OUTPUT.PUT_LINE ('Dept table opened.');
		close tcur;
		DBMS_OUTPUT.PUT_LINE ('Emp table closed.');
	ELSE
		RAISE_APPLICATION_ERROR (-20004, 'Table name is wrong');
	END IF;
END;

--CURSOR FOR LOOP WITH PARAMETERS
Declare
Cursor c1(Dno number) is select * from emp where deptno = dno;
begin
for empree in c1(10) loop;
dbms_output.put_line(empree.ename);
end loop;
end;

TRIGGERS

Trigger is a stored procedure which is called implicitly by oracle engine whenever a insert, update or delete statement is fired.

Advantages of database triggers:
—> Data is generated on it’s own
—> Replicate table can be maintained
—> To enforce complex integrity contraints
—> To edit data modifications
—> To autoincrement a field
etc..

Syntax: Create or replace trigger –triggername– [before/after] [insert/pdate/delete] on –tablename– [for each satement/ for each row] [when --condition--] plus..begin.and exception

Triggers are of following type: before or after trigger ….and for each row and for each statement trigger… before trigger is fired before insert/update/delete statement while after trigger is fired after insert/update/delete statement…for each row and for each statements triggers are self explainatory..

EXAMPLE

— A database trigger that allows changes to employee table only during the business hours(i.e. from 8 a.m to 5.00 p.m.) from monday to saturday. There is no restriction on viewing data from the table -CREATE OR REPLACE TRIGGER Time_Check BEFORE INSERT OR UPDATE OR DELETE ON EMP BEGIN IF TO_NUMBER(TO_CHAR(SYSDATE,’hh24′)) < 10 OR TO_NUMBER(TO_CHAR(SYSDATE,’hh24′)) >= 17 OR TO_CHAR(SYSDATE,’DAY’) = ‘SAT’ OR TO_CHAR(SYSDATE,’DAY’) = ‘SAT’ THEN RAISE_APPLICATION_ERROR (-20004,’YOU CAN ACCESS ONLY BETWEEN 10 AM TO 5 PM ON MONDAY TO FRIDAY ONLY.’); END IF; END;

Remember trigger can be dropped using Drop Trigger triggername ; statement…

PROCEDURES AND FUNCTIONS

procedure is a subprogram…which consists of a set of sql statement. Procedures are not very different from functions. A procedure or function is a logically grouped set of SQL and PL/SQL statements that perform a specific task. A stored procedure or function is a named pl/sql code block that have been compiled and stored in one of the oracle engines’s system tables.

To make a procedure or function dynamic either of them can be passed parameters before execution. A procedure or function can then change the way it works depending upon the parameters passed prior to its execution.

Procedures and function are made up of a declarative part, an executable part and an optional exception-handling part

A declaration part consists of declarations of variables. A executable part consists of the logic i.e. sql statements….and exception handling part handles any error during run-time

The oracle engine performs the following steps to execute a procedure or funtion….Verifies user access, Verifies procedure or funtion validity and executes the procedure or function. Some of the advantages of using procedures and functions are: security, performance, memory allocation, productivity, integrity.

Most important the difference between procedures and functions: A function must return a value back to the caller. A function can return only one value to the calling pl/sql block. By defining multiple out parameters in a procedure, multiple values can be passed to the caller. The out variable being global by nature, its value is accessible by any pl/sql code block including the calling pl/sql block.

Syntax for stored procedure:
CREATE OR REPLACE PROCEDURE [schema] procedurename (argument { IN, OUT, IN OUT} data type, ..) {IS, AS}
variable declarations; constant declarations; BEGIN
pl/sql subprogram body;
EXCEPTION
exception pl/sql block;
END;

Syntax for stored function:
CREATE OR REPLACE FUNCTION[schema] functionname(argument IN data type, ..) RETURN data type {IS, AS}
variable declarations; constant declarations; BEGIN
pl/sql subprogram body;
EXCEPTION
exception pl/sql block;
END;

The above syntax i think is self explainatory…but i will give u some details…IN : specifies that a value for the argument must be specified when calling the procedure or function. argument : is the name of an argument to the procedure or function. parentheses can be omitted if no arguments are present. OUT : specifies that the procedure passes a value for this argument back to its calling environment after execution. IN OUT : specifies that a value for the argument must be specified when calling the procedure and that the procedure passes a value for this argument back to its calling environment after execution. By default it takes IN. Data type : is the data type of an argument.

EXAMPLES

--PROCEDURE USING NO ARGUMENT..AND USING CURSOR
CREATE OR REPLACE PROCEDURE P2 IS
cursor cur1 is select * from emp;
begin
for erec in cur1
loop
dbms_output.put_line(erec.ename);
end loop;
end;

--PROCEDURE USING ARGUMENT
CREATE OR REPLACE PROCEDURE ME( X IN NUMBER) IS
BEGIN
dbms_output.put_line(x*x);
end;

sql> exec me(3);

--FUNCTION using argument
CREATE OR REPLACE FUNCTION RMT(X IN NUMBER) RETURN NUMBER IS
BEGIN
dbms_output.put_line(x*x);
--return (x*x);
end;

(make a block like this to run it.....)
begin
dbms_output.put_line(rmt(3));
end;

--CREATE A PROCEDURE THAT DELETE ROWS FROM ENQUIRY
--WHICH ARE 1 YRS BEFORE

Create or replace procedure myprocedure is begin
delete from enquiry where enquirydate <= sysdate - 1;
end;

--CREATE A PROCEDURE THAT TAKES ARGUMENT STUDENT NAME,
--AND FIND OUT FEES PAID BY THAT STUDENT

CREATE or REPLACE procedure me (namee in varchar) is
cursor c1 is select a.feespaiddate from feespaid a, enrollment b, enquiry c
where
c.enquiryno = b.enquiryno and
a.rollno = b.rollno and
c.fname = namee;
begin
for erec in c1
loop
dbms_output.put_line(erec.feespaiddate);
end loop;
end;

--SUM OF 2 NOS
CREATE or replace procedure p1 is
Declare
 a number;
 b number;
 c number;
Begin
 a:=50;
 b:=89;
 c:=a+b;
 dbms_output.put_line('Sum of '||a||' and '||b||' is '||c);
End;

--DELETION PROCEDURE
create or replace procedure myproc is
begin
delete from enquiry where fname='somdutt';
end;

--IN and OUT procedure example
Create or replace procedure lest ( a number, b out number) is
identify number;
begin
select ordid into identity from item where
itemid = a;
if identity < 1000 then
b := 100;
end if;
end l

--in out parameter eg
Create or replace procedure sample ( a in number, b in out number) is
identity number;
begin
select ordid, prodid into identity, b from item where itemid=a;
if b<600 then
b := b + 100;
end if;
end;

now procedure is called by passing parameter

declare
a number;
b number;
begin
sample(3000, b)
dbms_output.put_line(1th value of b is 11 b);
end ;

--SIMILAR EG AS BEFORE
create or replace procedure getsal( sal1 in out number) is
begin
select sal into sal1 from emp
where empno =  sal1;
end ;

now use the above in plsql block

declare
sal1 number := 7999;
begin
getsal(sal1);
dbms_output.put_line('The employee salary is' || sal1);
end ;

u can make a procedure and functions similarly…..also if u wanna drop a function then use drop function functionname and for procedure use drop procedure procedurename

PACKAGES

A package is an oracle object, which holds other objects within it. Objects commonly held within a package are procedures, functions, variables, constants, cursors and exceptions. Packages in plsql is very much similar to those packages which we use in JAVA……yeah!! java packages holds numerous classes..right!!!…

A package has 2 parts….. package specification and package body

A package specification part consists of all sort of declaration of functions and procedures while package body consists of codings and logic of declared functions and procedures…

EXAMPLE

--SIMPLEST EG

--specification
create or replace package pack2 is
function rmt(x in number) return number;
procedure rmt1(x in number);
end;

--body
create or replace package body pack2 is
function rmt(x in number) return number is
begin
return (x*x);
end;

procedure rmt1(x in number) is
begin
dbms_output.put_line(x*x);
end;
end;

(how to run.....)
exec packagename.procedurename
i.e.
exec pack2.rmt1(3);

As shown above u can put in complicated procedures and functions inside the package…I have just shown a simple example…u can easily modify the above code to fit your requirement……Just try out packages which includes cursors, procedures and functions..etc..Remeber pl/sql supports overloading…i.e. u can use the same function or procedure name in your application but with different no or type of arguments..