Views in SQL provide several advantages, including enhanced data security, reduced complexity, and improved data consistency. However, they can also introduce potential performance issues.

A view in SQL is essentially a virtual table that is derived from the result set of a query. It contains rows and columns similar to a regular table, with fields sourced from one or more actual tables in the database.

One of the primary benefits of using views is the added layer of security they offer. By creating a view, you can restrict access to the underlying tables, thereby minimizing exposure to sensitive data. For example, if you have a table containing confidential information like salaries or personal details, you can create a view that omits these sensitive columns. This allows users to interact with the view instead of the real table, effectively safeguarding the sensitive information.

Views also simplify the handling of complex data structures. When your database consists of multiple tables, retrieving data often requires numerous joins, which can be cumbersome. However, by creating a view that encapsulates these joins, you can access data from multiple tables with a single query, making data retrieval more efficient and user-friendly.

Furthermore, views help maintain data consistency. When multiple users access the same data set, a view can ensure uniformity. Any changes made to the underlying data are automatically reflected in the view, guaranteeing that all users see the same consistent information.

Despite their advantages, views do have some drawbacks. The most significant concern is potential performance issues. Since a view consists of a stored query, each time you access the view, the database must execute that query. This can lead to slower performance, particularly if the view is based on complex queries or large tables.

Additionally, in certain databases, views are read-only. This restriction means you cannot use them to update or insert data into the underlying tables, which can limit their utility in specific scenarios.

In summary, SQL views serve as virtual tables that enhance data security, reduce complexity, and promote consistent information across users by presenting data from one or more tables. However, they may result in decreased database performance due to the need to re-execute queries each time they are accessed, and they are sometimes read-only, which can constrain updates or inserts to the underlying tables.