Definition of Views:

i. Basically, a view is a single table derived from multiple tables or a logically representing subset of data.

ii. These other tables can be base tables or previously defined views.

iii. A view is considered to be a virtual table, in contrast to base tables, whose tuples are physically stored in database.

2. Implementation of View:

i. In SQL, the command to specify a view is CREATE VIEW. The view is given a (virtual) table name (or view name), a list of attribute names, and a query to specify the contents of the view.

Following is the syntax of view.

  CREATE VIEW viewname AS 

  SELECT column1, column2 

  FROM tablename

  WHERE columnname=expressionList;

ii. Consider a table Tbl_Employee with the fields Emp_ID, Emp_Name, Emp_DOB, Emp_Address, Emp_DateOfJoining, Emp_Gender, Emp_EmailID. Following is the view vw_EmployeeContactDetails which contains the name and Email ID of the employee.

  CREATE VIEW vw_EmployeeContactDetails

   SELECT Emp_Name, Emp_EmailID

   FROM Tbl_Employee

It results in the creation of view.

To fetch the items of view, a select statement can be written as follows:

   SELECT * FROM vw_EmployeeContactDetails

iii. If we do not need a view any more, we can use the DROP VIEW command to dispose of it. Syntax is

DROP VIEW viewname

Example:

To drop the view vw_EmployeeContactDetails, following SQL statement must be executed:

    DROP VIEW vw_EmployeeContactDetails