Understanding Contained Databases in SQL Server

A contained database in SQL Server is a database that is isolated from other databases and from the instance of SQL Server that hosts it. This isolation provides several advantages, particularly in managing and securing database environments. In this article, we will delve into the concept of contained databases, their benefits, and how they operate within SQL Server.

What is a Contained Database?

A contained database is a database that stores all its metadata directly within the database itself, as opposed to relying on the master database for metadata storage. This means that the database user is independent of the server-level logins, allowing for a more flexible and secure environment. Additionally, all settings related to the database, including its collation and various configurations, are defined within the database itself, eliminating the need for dependencies on the SQL Server login.

Benefits of Contained Databases

1. Isolation and Security

Welcome, Let's Talk About Database Isolation. Contained databases offer a level of isolation that enhances security. Since the metadata is stored within the database itself rather than the master database, the risk of metadata corruption or exposure is reduced. Furthermore, the lack of dependency on server-level logins makes the environment more secure, as there is no single point of failure related to user management on the SQL Server.

2. Portability

Another significant benefit of using contained databases is portability. Because all the necessary information is contained within the database, it can be easily moved between servers without requiring additional adjustments or dependencies. This makes it ideal for environments where database migration or replication is common.

3. Simplified Maintenance

The simplicity of maintenance is another advantage offered by contained databases. When all the metadata and settings are stored within the database itself, it simplifies the process of moving, restoring, and backing up the database. There is no need to manage server-level permissions or settings, which can streamline your database management processes.

How Contained Databases Work

Contained databases function by including all the necessary metadata and settings within the database itself. This means that when you create a contained database, you are essentially defining all the settings and configurations that are related to the database. For example, the collation, database settings, and any other metadata are stored in the database rather than the master database.

Creating a Contained Database

To create a contained database, you can use the following SQL command:

This command will create a new database called MyContainedDatabase with all necessary metadata stored within it, ensuring complete isolation and security.

Limitations and Considerations

While contained databases offer numerous benefits, there are some limitations and considerations to keep in mind.

1. Database Size

Contained databases can be larger in size due to the inclusion of all metadata within the database itself. This can impact storage requirements, especially for large databases.

2. Compatibility

Not all database objects and features are fully supported in contained databases. For instance, some advanced features such as certificate and asymmetric key management, and a few other specific functionalities might require dependencies on the master database.

When planning to use contained databases, it is important to thoroughly understand the limitations and ensure that they align with your specific requirements.

Conclusion

In conclusion, contained databases are a powerful feature in SQL Server that offer enhanced isolation, portability, and simplified maintenance. While there are some limitations to consider, the benefits of using contained databases can significantly improve the management and security of your database environments. Whether you need to ensure isolation, enhance security, or improve portability, contained databases are a valuable tool in your SQL Server arsenal.