Understanding the Purpose of a View in SQL

In SQL, a view serves the purpose of a virtual table that is based on the result-set of an SQL statement. This explanation might still seem a bit abstract, so let's break it down further.

When we talk about a 'view' in SQL, we refer to a temporary virtual table. It does not physically hold the data; instead, it draws data from the tables that it is based on. Therefore, a view is not a place to store data permanently. Nor is it used to insert new rows into a table or to define new data types.

A view represents a stored query or a predefined SQL query. Each time you invoke the view, you do not necessarily rerun the query; instead, the view fetches the data existing at the time the view was created.

Practical Applications of SQL Views

1. Simplicity: Views can simplify complex queries. You can create a view that presents the data in a more simplified form, thereby making the interaction with data easier.

2. Security: With views, you can control the level of data access. For instance, a view can be created to restrict access to sensitive information in a table while providing access to other data in the same table.

3. Modular Programming: Views can be used to encapsulate the naming and structure of tables. If a view is written to access certain columns or certain types of rows from the base table, modifications to the base table will not affect the view.

Best Practices for Using Views in SQL

While views are an efficient tool, incorrect handling of views can lead to performance issues. Here are a few best practices for using views:

1. Keep Views Simple: Multiple nested views can negatively impact performance. Prefer a single complex query over the complexity of nested views.

2. Avoid Using Views for Real-time Data: Given that views do not store data, they may not display real-time data unless refreshed.

3. Use Views for Data Security: Views are a powerful way to provide data security. Avoid giving table access whenever a view can provide the necessary data.

To sum up, views in SQL offer a powerful and flexible way to work with data. Used correctly, they can simplify programming tasks and provide a robust method for implementing data security.