What is a VIEW ?

A view in SQL is a virtual table that is created based on the result set of an SQL query. Unlike a table, a view does not store data physically in the database. Instead, it dynamically retrieves data from one or more underlying tables whenever it is queried. Here are some key points about views:

1. Definition: A view is essentially a saved SQL query that can be treated as a table. It contains rows and columns just like a real table, but the data is derived from the underlying base tables each time the view is accessed[1][2][4].

2. Creation: Views are created using the CREATE VIEW statement. The syntax typically looks like this:

   sql Copy

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

   For example, to create a view that shows all customers from Brazil, you would use:

   sql Copy

   CREATE VIEW Brazil_Customers AS
   SELECT CustomerName, ContactName
   FROM Customers
   WHERE Country = 'Brazil';
   ```[4][11].

3. Usage: Views can be used to simplify complex queries, provide a layer of security by restricting access to specific data, and present data in a specific format without altering the underlying tables. They can also be used to join data from multiple tables, aggregate data, and hide the complexity of the database schema from the end-users[1][2][5][9].

4. Advantages:

   • Security: Views can restrict access to specific rows and columns, thus providing a security layer.
   • Simplicity: They simplify complex queries by encapsulating them in a single view.
   • Space Efficiency: Since views do not store data, they save database storage space.
   • Up-to-date Data: Views always show the most current data from the underlying tables[1][2][9].

5. Limitations:

   • Performance: There can be a slight performance overhead because the view's query is executed every time the view is accessed.
   • Read-Only: Some views are read-...