The document discusses SQL views, which are saved SQL queries that act as virtual tables, allowing users to access specific data while maintaining security and reducing complexity. It provides examples on how to create, modify, and drop views, as well as perform insert, update, and delete operations on both tables and views. The key advantage of views is the ability to restrict access to sensitive data by permitting only a portion of the database to be visible to third parties.

1. Database Systems Lab
IT[244]
Lab #:10
FACULTY OF CS & IT
UNIVERSITY OF GUJRAT

2. SQL Views
• A view in SQL is just a saved SQL query.
• 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

3. SQL Views
• The main use of view is the security that its offer. A
third party may restricted to views only a portion of
database , While hiding the rest of sensitive data.
• View can be used as a mechanism to implement the
row and column level security.
• Reduce the data complexity

5. Creating a view
• Syntax
• Example
CREATE VIEW view_name AS
SELECT column_name(s)
FROM table_name
WHERE condition;
CREATE VIEW vw_employee
AS
SELECT first, last, address
FROM employee
Where emp_dept=‘IT’;

6. Creating a View
• Example
CREATE VIEW sup_orders
AS SELECT suppliers.supplier_id, orders.quantity, orders.price
FROM suppliers, orders
WHERE suppliers.supplier_id = orders.supplier_id and
suppliers.supplier_name = 'IBM';
This View (Create statement) would create a virtual table
based on the result set of the select statement. You can now
query the view as follows
Select * from sup_orders

7. Updating VIEW
• You can modify the definition of a VIEW without dropping it by
using the following
CREATE OR REPLACE VIEW vw_employee
AS
SELECT first, last, city
FROM employee
WHERE emp_dept=‘CS’;
View Modify – Example
CREATE or REPLACE VIEW sup_orders
AS SELECT suppliers.supplier_id, orders.quantity, orders.price
FROM suppliers, orders
WHERE suppliers.supplier_id = orders.supplier_id
and suppliers.supplier_name = 'Microsoft';

8. Alter VIEW
• You can modify the definition of a VIEW without dropping it by
using the following
ALTER VIEW view_name
AS SELECT columns
FROM table
WHERE condition;
View Alter - Example
ALTER VIEW sup_orders
AS SELECT suppliers.supplier_id, orders.quantity, orders.price
FROM suppliers, orders
WHERE suppliers.supplier_id = orders.supplier_id
and suppliers.supplier_name = 'Microsoft';

9. Dropping VIEW
• The syntax for dropping a VIEW :
DROP VIEW view_name;
• View Drop - Example
DROP VIEW sup_orders;

10. Insert View
• For table
Insert into employee
values (‘ali’,’raza’,’123’,’JPJ’,’Punjab’);
• For View
Insert into vw_employee
values(‘ali’,’raza’,’123’,’JPJ’,’Punjab’);

11. Update View
• For table
Update employee
set first=‘Ahmad’
where last=‘raza’;
• For View
Update employee
set first=‘Ahmad’
where last=‘raza’;

12. Delete View
• For table
Delete from employee
where first=‘Ahmad’;
• For View
Delete from employee
where first=‘Ahmad’;