What are the advantages and disadvantages of using a view in SQL?

Views in SQL offer advantages like data security, simplified complexity, and data consistency, but can also lead to performance issues.

A view in SQL is a virtual table based on the result-set of an SQL statement. It contains rows and columns, just like a real table, and fields in a view are fields from one or more real tables in the database.

One of the main advantages of using views is that they provide an extra layer of security. By creating a view, you can limit the degree of exposure of the underlying tables to the outer world. For instance, if you have a table with sensitive data like salaries or personal details, you can create a view that excludes these sensitive columns. Users can then access the view instead of the actual table, keeping the sensitive data secure.

Views also simplify the complexity of large data. If your database has multiple tables, joining them every time to fetch data can be a complex task. However, you can create a view that joins these tables. This way, you can retrieve data from multiple tables with a single query, making data handling more straightforward.

Moreover, views ensure data consistency. If multiple users are using the same set of data, creating a view can help maintain uniformity. Any changes made to the data are reflected in the view, ensuring all users see the same, consistent data.

However, views also have some disadvantages. The main one is that they can lead to performance issues. Since a view is a query stored as an object in a database, every time you run the view, the database needs to execute the query. This can slow down the system, especially if the view is based on complex queries or large tables.

Additionally, views are read-only in some databases. This means you can't use them to update or insert data into the underlying tables. This can limit their usefulness in some scenarios.

A-Level Computer Science Tutor Summary: In SQL, views act like virtual tables that help secure data, reduce complexity, and ensure consistent information across users by displaying data from one or more tables. However, they might slow down the database as they rerun queries each time they're accessed and are sometimes read-only, restricting updates or inserts to the underlying tables.