Views

A View in SQL is a virtual table based on the result-set of a `SELECT` statement. A view contains rows and columns, just like a real table, but it does not store the data itself. The data is stored in the underlying base tables from which the view is derived. When you query a view, the database engine executes the underlying `SELECT` statement to generate the results. Views offer several significant advantages. First, they provide simplification. You can encapsulate a complex query involving multiple joins and calculations into a simple view. Users can then query this view with a simple `SELECT * FROM my_view;` without needing to know the complex logic behind it. Second, they enhance security. You can create a view that shows only specific columns or rows from a table, hiding sensitive data from certain users. You can then grant permissions to the view instead of the underlying table. Third, they provide logical data independence. If you need to restructure the underlying tables (e.g., split a table), you can maintain the original view so that applications that use it don't break. This creates a stable, backward-compatible interface to the data. Views can be created using the `CREATE VIEW` statement. They are a powerful tool for both database administrators and developers to create reusable, secure, and simplified access to database data.