SQL VIEW Keyword

 The VIEW keyword in SQL is used to create a virtual table based on the result of a query. A view does not store the data physically but rather presents data from one or more underlying tables or other views. This can simplify complex queries and enhance security by restricting access to certain data.

Syntax:

CREATE VIEW view_name AS
SELECT column1, column2, ...
FROM table_name
WHERE condition;

• view_name: The name of the view you want to create.
• SELECT statement: The query that defines the content of the view.

Example:

CREATE VIEW EmployeeView AS
SELECT EmployeeID, FirstName, LastName, Department
FROM Employees
WHERE Department = 'Sales';

This will create a view called EmployeeView, showing only the employees from the Sales department. You can now query EmployeeView just like a regular table:

SELECT * FROM EmployeeView;

Key Points:

1. Virtual Table: A view behaves like a table but doesn't store data.
2. Read-Only or Updatable: Views can be either read-only or updatable, depending on the query used to create them and the database system.
3. Security: Views can be used to restrict access to sensitive data by showing only specific columns or rows from underlying tables.
4. Performance: Although views can simplify complex queries, excessive use of views or complex nested views may affect performance.

Altering or Dropping Views:

• Modify View:

  CREATE OR REPLACE VIEW view_name AS
  SELECT new_column1, new_column2
  FROM new_table;
  

• Drop View:

  DROP VIEW view_name;
  

Views are a powerful tool in SQL to abstract complexity and improve data security and management.