Views in SQL

Understanding SQL Views with Examples

Introduction to SQL Views

Views in SQL are virtual tables that allow you to encapsulate complex queries and present the results as if they were a real table.

Sample Table: Employees

EmployeeID	FirstName	LastName	Department
101	Alice	Smith	HR
102	Bob	Jones	IT

Creating a View

Views can be created using the CREATE VIEW statement:

CREATE VIEW EmployeeNames AS
SELECT EmployeeID, FirstName, LastName
FROM Employees;
    

Using a View

You can query a view like you would query a table:

SELECT * FROM EmployeeNames;
    

Output:

EmployeeID	FirstName	LastName
101	Alice	Smith
102	Bob	Jones

Updating a View

Views can be used to simplify complex updates:

CREATE OR REPLACE VIEW ITEmployees AS
SELECT * FROM Employees
WHERE Department = 'IT';
    

Advantages of Views

• Hide complex query logic
• Restrict data access
• Provide an additional layer of security

Modifying a View

Views can be modified with the CREATE OR REPLACE VIEW statement:

CREATE OR REPLACE VIEW EmployeeNames AS
SELECT EmployeeID, FirstName, LastName
FROM Employees
WHERE Department = 'HR';
    

Deleting a View

Views can be deleted using the DROP VIEW statement:

DROP VIEW EmployeeNames;
    

Conclusion

SQL views provide a powerful way to simplify complex queries and enhance data security. They act as virtual tables, allowing you to present data from multiple tables as a single entity.