DBMS UNIT 9.pptx..................................

Database Management System
UNIT-9 PL/SQL Concepts
Computer Science & Engineering
Dr. Vishwanath
PARUL INSTITUTE OF ENGINEERING & TECHNOLOGY
FACULTY OF ENGINEERING & TECHNOLOGY
PARUL UNIVERSITY

Views
PL/SQL Block
Cursors
Triggers
Stored Procedures
Store Functions

Views
A PL/SQL view is a virtual table that contains data from one or
more tables.
Views are used to provide security or simplify complex queries.
Creating a View:
To create a view, you use the CREATE VIEW statement as
follows:
CREATE VIEW view_name AS
SELECT column1, column2,...
FROM table_name
WHERE condition;

Views
For example, to create a view that displays all employees in the sales
department.
CREATE VIEW sales_employees AS
SELECT first_name, last_name
FROM employees
WHERE department = 'Sales';
To display the view, you use the SELECT statement as follows:
SELECT * FROM view_name;
For example, to display all employees in the sales department:
SELECT * FROM sales_employees;

Views
Updating a View
To update data in a view, you use the UPDATE View statement.
For example, to increase the salary of all employees in the sales
department by 10%.
UPDATE sales_employees SET salary = salary * 1.1;

Views
Modifying a View
You can modify an existing view by using the CREATE OR REPLACE
VIEW statement.
This statement first drops the existing view and then creates it again.
For example, to modify the sales_employees view so that it displays all
employees in the sales or marketing departments
CREATE OR REPLACE VIEW sales_employees AS
SELECT first_name, last_name
FROM employees
WHERE department IN ('Sales', 'Marketing');

Views
 The view is a virtual table. It does not physically exist. Rather, it is created by a
query joining one or more tables.
 A view contains rows and columns, just like a real table
 The fields in a view are fields from one or more real tables in the database
Creating an SQL VIEW
Syntax:
CREATE VIEW view_name AS
SELECT column_name(s)
FROM table_name
WHERE condition;

Views
View Creation – Example
1. CREATE VIEW transaction_view
AS SELECT acc_no, tr_date,amt from transaction;
2. Create view account_view
AS SELECT a.acc_no,a.balance,l.loan_amt,l.interest_rate from account a, loan l where
a.acc_no=l.acc_no and a.city=‘Ahmedabad’;
The above views would create a virtual table based on the
result set of the select statement. To show created views:
1. SELECT * FROM transaction_view;
2. SELECT * FROM account_view;

Views
1. Create or Replace view account_view
AS SELECT a.acc_no,a.balance,l.loan_amt,l.interest_rate,
l.remaining_loan from account a, loan l where a.acc_no=l.acc_no and
a.city=‘Vadodara’;
Updating View
You can modify the definition of a VIEW without dropping it by using the
following syntax:
CREATE OR REPLACE VIEW view_name
AS SELECT columns
FROM table
WHERE predicates;

Views
Deleting View
The syntax for dropping a VIEW :
DROP VIEW view_name;
View Drop - Example
DROP VIEW transaction_view;

Views
Question: Can you update the data in an view?
Answer : A view is created by joining one or more tables. When you update
record(s) in a view, it updates the records in the underlying tables that make up the
View. So, yes, you can update the data in View providing you have the proper
privileges to the underlying tables.
Question: Does the SQL View exist if the table is dropped from the database?
Answer: Yes, View continues to exist even after one of the tables (that the SQL View
is based on) is dropped from the database. However, if you try to query the View
after the table has been dropped, you will receive a message indicating that the
View has errors.

Trigger
 A trigger is a block structure which is fired when a DML statements
like Insert, Delete, Update is executed on a database table. A trigger
is triggered automatically when an associated DML statement is
executed.
Syntax of Triggers
CREATE [OR REPLACE ] TRIGGER trigger_name
{BEFORE | AFTER}
{INSERT [OR] | UPDATE [OR] | DELETE}
[OF col_name]
ON table_name
[REFERENCING OLD AS o NEW AS n]
[FOR EACH ROW]
WHEN (condition) ;

Trigger
Creating Trigger
1. CREATE TRIGGER deleted_details
BEFORE
DELETE on loan
FOR EACH ROW
2. CREATE TRIGGER inserted_details
after
insert on transaction
FOR EACH ROW

Trigger
Creating Trigger
3. CREATE TRIGGER updated_details
BEFORE
UPDATE on account
FOR EACH ROW when name=‘Patel Hiren’;
Deleting Trigger
Drop trigger inserted_details on transaction;

Trigger
 The syntax for a dropping a Trigger is:
DROP TRIGGER trigger_name ON tbl_name;
 The syntax for a disabling a Trigger is:
ALTER TRIGGER trigger_name DISABLE;
 The syntax for a enabling a Trigger is:
ALTER TRIGGER trigger_name ENABLE;

PL/SQL
Procedural Language – SQL: An extension to SQL with design
features of programming languages (procedural and object
oriented)

PL/SQL
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
 There are 2 types of Datatypes:
1. Scalar (Char, Varchar2, Date and Number)
2. Composite (%rowtype)
 All Variables required to be used in the program must be declared before
their use. Variable names cannot be table, column and keyword names.
 Assignment Operator is denoted as “:=” and each statement of PL/SQL ends
with “;”.
 Dbms_Output.Put_Line() is used for printing Output.
 &Variable_Name :Variable Name is use to take input from the user.

PL/SQL
1. IF …THEN…ELSE
IF <condition> THEN
<Code>
ELSEIF <condition> THEN
<Code>
ELSE
<Code>
ENDIF;
2. CASE…
CASE
WHEN VARIABLE = VALUE THEN
<Code>
WHEN VARIABLE = VALUE THEN
<Code>
ELSE
<Code>
END CASE;
 Conditional Statements

PL/SQL
1. Simple Loop
Loop
<Code>
Exit when <Cond>
End Loop;
2. While Loop
While <Condition>
Loop
<Code>
End Loop;
 Types of Loops
3. For Loop
FOR <Variable> IN <Min> .. <Max>
Loop
<Code>
End Loop;
4. For Loop
FOR <Variable> IN REVERSE <Min> ..
<Max>
Loop
<Code>
End Loop;

PL/SQL Examples
Write a PL/SQL block to add 2 numbers
declare
x number(5);
y number(5);
z number(7);
begin
x:=10;
y:=20;
z:=x+y;
DBMS_OUTPUT.PUT_LINE('Sum is '||z);
end;

PL/SQL Examples
Write a PL/SQL block to find maximum of 2 numbers
declare
x number(5);
y number(5);
begin
x:=10;
y:=20;
if x > y then
DBMS_OUTPUT.PUT_LINE(‘x is greater than y');
else
DBMS_OUTPUT.PUT_LINE(‘ y is greater than x');
end if;
end;

PL/SQL Examples
Write a PL/SQL
block to find area of
rectangle, square
and circle
declare
area_c number(6, 2) ;
radius number(1) := 3 ;
area_r number(6) ;
area_s number(6) ;
length number(2) := 5 ;
width number(2) := 4 ;
pi constant number(3, 2) := 3.14;
begin
area_c := pi * radius * radius;
DBMS_OUTPUT.PUT_LINE('Circle area = ' || area_c);
area_r := length * width;
DBMS_OUTPUT.PUT_LINE('Rectangle area = ' || area_r);
area_s := length * length;
DBMS_OUTPUT.PUT_LINE('Square area = ' || area_s);
end;

PL/SQL Examples
Write a PL/SQL block to print the sum of Numbers from 1
to 100
declare
a number;
sum1 number :=0;
begin
a:=1;
loop
sum1:=sum1+a;
a:=a+1;
exit when (a>100);
end loop;
DBMS_OUTPUT.PUT_LINE('sum of 1 to 100 is '||sum1);
end;

PL/SQL Examples
Write a PL/SQL program for inserting even numbers in EVEN table and odd number in ODD table from
number 1 to 50.
begin
for i in 1..50
loop
if mod(i,2) = 0 then
insert into EVEN values (i);
end if;
end loop;
for i in 1..50
loop
if mod(i,2)!= 0 then
insert into ODD values (i);
end if;
end loop;
end;

PL/SQL Examples
Write a PL/SQL block to print the given number is prime or not
declare
num number;
i number:=1;
c number:=0;
begin
num:=#
for i in 1..num
loop
if((mod(num,i))=0)
then
c:=c+1;
end if;
end loop;
if(c>2)
then
DBMS_OUTPUT.PUT_LINE(num||' not a prime');
else
DBMS_OUTPUT.PUT_LINE(num||' is prime');
end if;
end;

PL/SQL
%RowType
Variable Name TableName%RowType
acc account%RowType;
- This “acc” variable will have complete structure of the table account. Any column
of account table can be referred using “acc” variable
DECLARE
acc account%RowType;
BEGIN
select * into acc from account where acc_no=‘A001’;
DBMS_OUTPUT.PUT_LINE (acc.name); = “Patel Hiren”
DBMS_OUTPUT.PUT_LINE (acc.city); = “Mehsana”
DBMS_OUTPUT.PUT_LINE (acc.balance); = 50000
DBMS_OUTPUT.PUT_LINE (acc.loan_taken); = “YES”
END;

Cursor
 A cursor is a private set of records.
 A cursor is a temporary work area created in the system memory when a SQL
statement is executed. A cursor contains information on a select statement and
the rows of data accessed by it.
 This temporary work area is used to store the data retrieved from the database,
and manipulate this data. A cursor can hold more than one row, but can process
only one row at a time. The set of rows the cursor holds is called the active set.
 There are 2 types of Cursors:
1. Implicit Cursor: Created automatically for every query in SQL.
2. Explicit Cursor: Created manually by the programmer.

Cursor
Cursor Attributes
cursorname%ROWCOUNT Rows returned so far
cursorname%FOUND One or more rows retrieved
cursorname%NOTFOUND No rows found
cursorname%ISOPEN Is the cursor open

Cursor
Explicit Cursor
• Declare the cursor
• Open the cursor
• Fetch a row
• Test for end of cursor
• Close the cursor

Cursor
Explicit Cursor Example
DECLARE
CURSOR account_cursor IS SELECT * from account;
acc account%rowtype
BEGIN
DBMS_OUTPUT.PUT_LINE ('******************');
OPEN account_cursor;
FETCH account_cursor into acc;
WHILE account_cursor % Found
LOOP
DBMS_OUTPUT.PUT_LINE (acc.name);
DBMS_OUTPUT.PUT_LINE (acc.city);
DBMS_OUTPUT.PUT_LINE (acc.balance);
DBMS_OUTPUT.PUT_LINE (acc.loan_taken)
DBMS_OUTPUT.PUT_LINE ('******************');
FETCH account_cursor into acc;
END LOOP;
CLOSE account_cursor;
END;

Stored Procedure
 A program unit is a self-contained group of program statements that can be used within a
large program
 Stored PL/SQL program units are program units that other PL/SQL program can reference
and that other database users can use and execute.
 Can receive multiple input parameters and return multiple output values (or no output
values) and perform DML Commands
CREATE [OR REPLACE] PROCEDURE procedure_name [ (parameter
mod datatype [,parameter]) ]
IS
[local variable declaration_section]
BEGIN
executable_section
[EXCEPTION
exception_section]
END [procedure_name];

Stored Procedure
 The header section defines:
1. The procedure name (name should be unique )
2. The parameters that the procedure receives or delivers
(IN, OUT, IN OUT)
3. IS keyword: follows the parameters list
4. The local procedure variables
 Create or replace: instructs the DBMS to create the procedure if it does it exists, otherwise; it replaces the
existing one
 OR REPLACE clause is optional. But if omitted and a procedure exists with the same name, an error occurs
 Parameter name, mod and data type are enclosed in parentheses, each is separated by a comma.
 Parameter mod: describes how the procedure change the value. It can be:
1. IN: passed parameter is a Read only value. Cannot be changed by the procedure
2. OUT: write-only value. Always comes on the left side of an assignment statement
3. IN OUT: its value can be changed

Stored Procedure
EXAMPLE:
Create or replace procedure account_update
(
curr_acc_no IN varchar2,
curr_name IN varchar2,
curr_balance IN number
)
IS
BEGIN
update account
set balance = curr_balance
where
acc_no = curr_acc_no and
name = curr_name;
COMMIT;
END;
The Following Stored
Procedure updates the
balance of the account
for a given account
number and name of
the account.
Execute account_update(‘A001’,’Patel’,125000);
Command to
Execute the Store
Procedure

Function
 A function is similar to a procedure, except that it returns a single value.
 Functions can accept one, many, or no parameters, but a function must have a
return clause in the executable section of the function.
 The datatype of the return value must be declared in the header of the function.
 The syntax for creating a function is as follows:
CREATE [OR REPLACE] FUNCTION function_name
(parameter list)
RETURN datatype
IS
BEGIN
<body>
RETURN (return_value);
END;

Function
EXAMPLE:
Create or replace function account_det
(account_num varchar2)
RETURN varchar2
AS
acc_name varchar2(30);
BEGIN
select name into acc_name from
account where acc_no=account_num;
RETURN acc_name;
END;
The Following
Function will
fetch the name of
the account for a
given account
number.
DECLARE
acc_name VARCHAR2(30);
BEGIN
acc_name := account_det(&account_num);
DBMS_OUTPUT.PUT_LINE(acc_name);
END;
2 Ways to Execute the Function:
Select
account_det(‘A001’)
from account;

DBMS UNIT 9.pptx..................................

More Related Content

Similar to DBMS UNIT 9.pptx.................................. (20)

Recently uploaded (20)

DBMS UNIT 9.pptx..................................