Zend Anwar

What is view?

A view is, in essence, a virtual table. It does not physically exist. Rather, it is created by a query joining one or more tables. . A view is actually a composition of a table in the form of a predefined SQL query.

A view can contain all rows of a table or select rows from a table. A view can be created from one or many tables which depend on the written SQL query to create a view.

 How to create a view:

Creating a VIEW

The syntax for creating a view is:

CREATE VIEW view_name AS
SELECT columns
FROM table
WHERE predicates;

Example:

CREATE VIEW sub_employee AS
SELECT job.job_id, employee.name, employee.salary, employee. employee_id, employee.dept, FROM job, employee
WHERE job.job_id = employee.employee_id
and employee.dept = ‘software’;

This would create a virtual table based on the result set of the select statement. You can now query the view as follows:

SELECT *
FROM sub_employee;

How to update view:

Updating a view

You can update a view without dropping it by using the following syntax:

CREATE OR REPLACE VIEW view_name AS
SELECT columns
FROM table
WHERE predicates;

Example:

CREATE or REPLACE VIEW sup_orders AS
SELECT job.job_id, employee.name, employee.salary, employee. employee_id, employee.dept, FROM job, employee
WHERE job.job_id = employee.employee_id
and employee.dept = ‘software’;

How to drop view:

Dropping a view

The syntax for dropping a view is:

DROP VIEW view_name;

Example:

DROP VIEW sub_employee;