Introduction to PL/SQL

PL/SQL
Agenda
2
1. Introduction to PL/SQL
2. PL/SQL Architecture
3. Basic Syntax
4. PL/SQL – Procedures
5. PL/SQL – Functions
6. PL/SQL – Cursors
7. PL/SQL – Packages
8. Conclusion

PL/SQL 3
Introduction to PL/SQL PL/SQL Architecture Basic Syntax PL/SQL – Procedures PL/SQL – Functions PL/SQL – Cursors PL/SQL – Packages Conclusion
What is PL/SQL?
 PL SQL basically stands for "Procedural Language extensions to SQL“ . PL/SQL allows
the programmer to write code in procedural format
 It combines the data manipulation power of SQL with the processing power of
procedural language to create a super powerful SQL queries
 It allows the programmers to instruct the compiler 'what to do' through SQL and
'how to do' through its procedural way
 PL/SQL was developed Oracle’s corporation . It is a proprietary language

PL/SQL 4
PL/SQL Architecture

PL/SQL 5
PL/SQL ENGINE
 PL/SQL engine is the component where the actual processing of the codes takes place
 PL/SQL engine separates PL/SQL units and SQL part in the input
 The separated PL/SQL units will be handled with the PL/SQL engine itself
 The SQL part will be sent to database server where the actual interaction with
database takes place.
 It can be installed in both database server and in the application server

PL/SQL 6
SQL VS PL/SQL
SQL PL/SQL
SQL is a single query that is used to perform DML and
DDL operations
PL/SQL is a block of codes that used to write the
entire program blocks/ procedure/ function, etc
It is declarative, that defines what needs to be done,
rather than how things need to be done
PL/SQL is procedural that defines how the things
needs to be done
Execute as a single statement Execute as a whole block
Mainly used to manipulate data Mainly used to create an application
Interaction with Database server No interaction with the database server
Cannot contain PL/SQL code in it It is an extension of SQL, so it can contain SQL inside
it.

PL/SQL 7
PL/SQL Block Types
Anonymous
DECLARE
BEGIN
-statements
EXCEPTION
END;
Procedure
PROCEDURE <name>
IS
BEGIN
-statements
EXCEPTION
END;
Function
FUNCTION <name>
RETURN <datatype>
IS
BEGIN
-statements
EXCEPTION
END;

PL/SQL 8
PL/SQL BLOCK STRUCTURE
DECLARE (optional)
- variable declarations
BEGIN (required)
- SQL statements
- PL/SQL statements or sub-blocks
EXCEPTION (optional)
- actions to perform when errors occur
END; (required)

PL/SQL 9
Example
DECLARE
v_first_name VARCHAR2(35);
v_last_name VARCHAR2(35);
BEGIN
SELECT first_name, last_name INTO v_first_name, v_last_name FROM student WHERE student_id = 123;
DBMS_OUTPUT.PUT_LINE ('Student name: '||v_first_name||' ‘|| v_last_name);
EXCEPTION
WHEN NO_DATA_FOUND THEN DBMS_OUTPUT.PUT_LINE ('There is no student with '|| 'student id 123’);
END;

PL/SQL 10
Example for Nested Blocks
DECLARE
-- Global variables
num1 number := 95;
num2 number := 85;
BEGIN
dbms_output.put_line('Outer Variable num1: ' || num1);
dbms_output.put_line('Outer Variable num2: ' || num2);
DECLARE
-- Local variables
num1 number := 195;
num2 number := 185;
BEGIN
dbms_output.put_line('Inner Variable num1: ' || num1);
dbms_output.put_line('Inner Variable num2: ' || num2);
END;
END;

PL/SQL 11
Introduction to PL/SQL PL/SQL Architecture Basic Syntax PL/SQL –
Procedures
PL/SQL – Functions PL/SQL – Cursors PL/SQL – Packages Conclusion
Subprogram
A subprogram is a program unit/module that performs a particular task.
PL/SQL subprograms are named PL/SQL blocks that can be invoked with a set of parameters. PL/SQL provides
two kinds of subprograms −
Functions − These subprograms return a single value; mainly used to compute and return a
value.
Procedures − These subprograms do not return value directly; mainly used to perform an
action.
A subprogram can be created −
1. At the schema level
2. Inside a package
3. Inside a PL/SQL block

PL/SQL 12
Procedures
Syntax:
CREATE [OR REPLACE] PROCEDURE procedure_name
[(parameter_name [IN | OUT | IN OUT] type [, ...])]
{IS | AS}
BEGIN
< procedure_body >
END procedure_name;
Creating a Procedure
Executing a Procedure
A standalone procedure can be called in two ways −
1.Using the EXECUTE keyword
eg:
2.Calling the name of the procedure from a PL/SQL block
eg: BEGIN
greetings;
END;
EXECUTE
greetings;

PL/SQL 13
Procedures
Example
DECLARE
a number;
b number;
c number;
Create or replace PROCEDURE findMin(x IN number, y IN number, z OUT number) IS
BEGIN
IF x < y THEN
z:= x;
ELSE
z:= y;
END IF;
END;
BEGIN
a:= 23;
b:= 45;
findMin(a, b, c);
dbms_output.put_line(' Minimum of (23, 45) : ' || c);
END ;

PL/SQL 14
Procedures
Example
DECLARE
a number;
b number;
c number;
Create or replace PROCEDURE findMin(x IN number, y IN number, z OUT number) IS
BEGIN
IF x < y THEN
z:= x;
ELSE RESULT:
z:= y;
END IF;
END;
BEGIN
a:= 23;
b:= 45;
findMin(a, b, c);
dbms_output.put_line(' Minimum of (23, 45) : ' || c);
END ;
Minimum of (23, 45) : 23
PL/SQL procedure successfully completed

PL/SQL 15
Creating a Function
Syntax:
CREATE [OR REPLACE] FUNCTION function_name
[(parameter_name [IN | OUT | IN OUT] type [, ...])]
RETURN datatype
IS
BEGIN
<body>
RETURN (return_value);
END;

PL/SQL 16
Example
Prob : Recursive function to calculate factorial for a number
DECLARE
num number;
factorial number;
CREATE OR REPLACE FUNCTION fact(x number)
RETURN number
IS
f number;
BEGIN
IF x=0 THEN
f := 1;
ELSE
f := x * fact(x-1);
END IF;
RETURN f;
END;
BEGIN
num:= 6;
factorial := fact(num);
dbms_output.put_line(' Factorial '|| num || ' is ' || factorial);
END;

PL/SQL 17
Example
Prob : Recursive function to calculate factorial for a number
DECLARE
num number;
factorial number;
CREATE OR REPLACE FUNCTION fact(x number)
RETURN number
IS
f number;
BEGIN
IF x=0 THEN
f := 1;
ELSE RESULT :
f := x * fact(x-1);
END IF;
RETURN f;
END;
BEGIN
num:= 6;
factorial := fact(num);
dbms_output.put_line(' Factorial '|| num || ' is ' || factorial);
END;
Factorial 6 is 720
PL/SQL procedure successfully completed

PL/SQL 18
Cursors
 Oracle creates a memory area, known as the context area, for processing an
SQL statement, which contains all the information needed for processing the
statement; for example, the number of rows processed, etc.
 A cursor is a pointer to this context area. PL/SQL controls the context area
through a cursor. A cursor holds the rows (one or more) returned by a SQL
statement. The set of rows the cursor holds is referred to as the active set.
 There are two types of cursors
 Implicit cursors
 Explicit cursors

PL/SQL 19
Implicit cursors
 Implicit cursors are automatically created by Oracle whenever an SQL statement
is executed, when there is no explicit cursor for the statement. Programmers
cannot control the implicit cursors and the information in it
 Whenever a DML statement (INSERT, UPDATE and DELETE) is issued, an
implicit cursor is associated with this statement. For INSERT operations,
the cursor holds the data that needs to be inserted. For UPDATE and
DELETE operations, the cursor identifies the rows that would be affected
 The most recently opened implicit cursor is SQL cursor
 During the processing of an implicit cursor, Oracle automatically performs the
OPEN, FETCH, and CLOSE operations

PL/SQL 20
Cursor Attributes
• cursorname%ROWCOUNT Rows returned so far
• cursorname%FOUND Returns TRUE , if One or more rows affected
• cursorname%NOTFOUND Returns TRUE, If No rows affected
• Cursorname%ISOPEN Is the cursor open

PL/SQL 21
Example
DECLARE
total_rows number(2);
BEGIN
UPDATE customers
SET salary = salary + 500;
IF sql%notfound THEN
dbms_output.put_line('no customers selected');
ELSIF sql%found THEN
total_rows := sql%rowcount;
dbms_output.put_line( total_rows || ' customers selected ');
END IF;
END;

PL/SQL 22
Explicit Cursor
 Explicit cursors are programmer-defined cursors for gaining more control over the
context area.
 An explicit cursor should be defined in the declaration section of the PL/SQL Block.
 It is created on a SELECT Statement which returns more than one row.
 The process of working with an explicit cursor consists of the following steps:
1. Declaring the cursor : CURSOR cursor_name is select statement;
2. Opening the cursor : open cursor_name;
3. Fetching the cursor : FETCH cursor_name into variables;
4. Closing the cursor : CLOSE cursor_name;

PL/SQL 23
Example
DECLARE
c_id customers.id%type;
c_name customers.Name%type;
c_addr customers.address%type;
CURSOR c_customers is
SELECT id, name, address FROM customers;
BEGIN
OPEN c_customers;
LOOP
FETCH c_customers into c_id, c_name, c_addr;
EXIT WHEN c_customers%notfound;
dbms_output.put_line(c_id || ' ' || c_name || ' ' || c_addr);
END LOOP;
CLOSE c_customers;
END;

PL/SQL 24
Introduction to PL/SQL PL/SQL Architecture Basic Syntax PL/SQL – Procedures PL/SQL – Functions PL/SQL – Cursors PL/SQL –
Packages
Conclusion
Packages
 A package is a collection of PL/SQL objects grouped under one package name
 Packages include procedures, functions, cursors, declarations, types, and variables
 Enables the oracle server to read multiple objects into memory simultaneously
 A package will have two mandatory parts:
1. Package specification
2. Package body or definition

PL/SQL 25
Packages
Conclusion
Components of package

PL/SQL 26
Packages
Conclusion
Package specification
It DECLARES the types, variables, constants, exceptions, cursors, and
subprograms that can be referenced from outside the package.
In other words, it contains all information about the content of the package, but
excludes the code for the subprograms.
All objects placed in the specification are called public objects. Any subprogram
not in the package specification but coded in the package body is called a private
object

PL/SQL 27
Packages
Conclusion
Package specification
SYNTAX:
CREATE OR REPLACE PACKAGE package_name
AS
[ declarations of variables and types ]
[ specifications of cursors ]
[ specifications of modules ]
END [ package_name ];
EG:
CREATE OR REPLACE PACKAGE cust_sal AS
PROCEDURE find_sal(c_id customers.id%type);
END cust_sal;

PL/SQL 28
Packages
Conclusion
Package body
 The package body has the codes for various methods declared in the package
specification and other private declarations, which are hidden from the code
outside the package
 SYNTAX:
CREATE OR REPLACE PACKAGE BODY package_name
IS
[ declarations of variables and types ]
[ specification and SELECT statement of cursors ]
[ specification and body of modules ]
BEGIN
executable statements
END [ package_name ];

PL/SQL 29
Packages
Conclusion
EXAMPLE
CREATE OR REPLACE PACKAGE BODY cust_sal AS
PROCEDURE find_sal(c_id customers.id%TYPE) IS
c_sal customers.salary%TYPE;
BEGIN
SELECT salary INTO c_sal
FROM customers
WHERE id = c_id;
dbms_output.put_line('Salary: '|| c_sal);
END find_sal;
END cust_sal;

PL/SQL 30
Conclusion
PL/SQL has four major advantages
1 . Tight integration with SQL
2 . High performance
3 . Full portability
4 . Tight security

dbms_output.put_line(‘THANK YOU!!!’);

Introduction to PL/SQL

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