SQL Server Compatibility Levels
Updated: 6 days ago
Whether you are a small business owner or work at an enterprise organization, effective management of your SQL Server is integral for successful data operations. As new versions of Microsoft’s database engine come out, there is an option to set the compatibility level so that databases can be configured to work with the version and still maintain backward compatibility. This post will discuss what SQL Server Compatibility Levels are, why they are important and how they help ensure that databases remain compatible across different versions. We’ll also look at how administrators can leverage this feature in order to optimize their networks for peak performance levels. By understanding these concepts, organizations will be well-equipped to handle upgrade paths while keeping pace with rapid technology changes without sacrificing stability.
SQL Server Compatibility Levels
Whether you are a small business owner or work at an enterprise organization, effective management of your SQL Server is integral for successful data operations. As new versions of Microsoft’s database engine come out, there is an option to set the compatibility level so that databases can be configured to work with the version and still maintain backward compatibility. This post will discuss what SQL Server Compatibility Levels are, why they are important and how they help ensure that databases remain compatible across different versions. We’ll also look at how administrators can leverage this feature in order to optimize their networks for peak performance levels. By understanding these concepts, organizations will be well-equipped to handle upgrade paths while keeping pace with rapid technology changes without sacrificing stability.
What are SQL Server Compatibility Levels and why they are important
SQL Server Compatibility Levels serve a crucial role in ensuring seamless integration and optimal performance in diverse database environments. These levels determine the specific SQL Server version behaviors supported by a database, facilitating backward compatibility and smooth transitions during version upgrades. Maintaining an effective compatibility framework is essential for organizations to protect their existing applications from potential disruptions, optimize database functionalities, and promote efficient resource utilization.
By setting an appropriate compatibility level, DBAs can continue harnessing the benefits of earlier SQL Server iterations while embracing the latest innovations and features, empowering a harmonious ecosystem that caters to an organization's diverse needs. As such, SQL Server Compatibility Levels act as a critical bridge to align legacy applications with current technological advancements, fostering continuous improvement and sustainable progress in the realm of data management.
Here are the available SQL Server Compatibility Levels:
SQL Server 6.5 (60)
SQL Server 7.0 (70)
SQL Server 2000 (80)
SQL Server 2005 (90)
SQL Server 2008 (100)
SQL Server 2012 (110)
SQL Server 2014 (120)
SQL Server 2016 (130)
SQL Server 2017 (140)
SQL Server 2019 (150)
The default compatibility level for a new database is the current version of SQL Server, but it can be changed to any of the available levels. The compatibility level affects certain database behaviors, such as syntax and query optimization, so it's important to choose the right level for your needs.
How to set the compatibility level of a database in Microsoft SQL Server
Knowing how to set the compatibility level of a database in Microsoft SQL Server is an important part of managing your data. The SQL Server Compatibility Level feature allows you to ensure all objects and data within a given database are compatible with a specific version of SQL Server, thus preventing any potential compatibility issues. To use this feature, you will have to use the ALTER DATABASE statement in Transact-SQL with the option COMPATIBILITY_LEVEL set to whatever desired version you wish your database to operate at. Careful consideration should be made when setting the compatibility level, as changing the level may affect some functionality available in that version.
You can set the compatibility level for a database in SQL Server Management Studio (SSMS) by following these steps:
Connect to the SQL Server instance in SSMS.
Expand the Databases folder.
Right-click on the database you want to modify and select Properties.
In the Database Properties window, select the Options page.
Scroll down to the Compatibility Level option and select the desired level from the dropdown menu.
Click OK to save the changes.
Alternatively, you can also use a T-SQL command to change the compatibility level of a database:
USE [database_name]
GO
ALTER DATABASE [database_name] SET COMPATIBILITY_LEVEL = {compatibility_level}
GOReplace "database_name" with the name of the database you want to modify, and "compatibility_level" with the desired level number. For example, to set the compatibility level to SQL Server 2012 (110), you would use:
USE [database_name]
GO
ALTER DATABASE [database_name] SET COMPATIBILITY_LEVEL = 110
GOMake sure to test your application after changing the compatibility level, as it may affect the behavior of certain features and queries.
When Does Changing compatibility levels Take Effect?
Changing the compatibility level of a database takes effect immediately for new connections to the database. For existing connections, the new compatibility level will take effect after the next time the connection is established.
When the compatibility level is changed, it affects the behavior of certain database features and query optimizations. Therefore, it's important to thoroughly test the database and any applications that use it after changing the compatibility level to ensure that everything is still functioning as expected.
Note that changing the compatibility level of a database is a one-way operation. Once you change the compatibility level to a lower version, you cannot change it back to a higher version. Therefore, it's recommended to backup the database before changing the compatibility level to ensure that you have a copy of the database at the previous level.
Troubleshooting issues when working with SQL Server Compatibility Levels
When working with SQL Server Compatibility Levels, there are some issues that may arise, and here are some troubleshooting tips to help you resolve them:
Queries not working: If you're experiencing issues with queries not working after changing the compatibility level, it may be because some query syntax or behavior has changed. Check the Microsoft documentation for the specific compatibility level to identify the changes in syntax and behavior that may affect your queries.
Poor query performance: If you're experiencing slow query performance after changing the compatibility level, it may be because the query optimizer is using a different execution plan. Try updating the statistics for the affected tables, and check the query plan to identify any changes in the execution plan.
Missing features: If you're missing features after changing the compatibility level, it may be because the feature is not supported in the new level. Check the Microsoft documentation to identify the features that are not available in the new level.
Backup and restore issues: If you're having issues restoring a database backup after changing the compatibility level, it may be because the backup was created at a higher compatibility level. In this case, you will need to either restore the backup to a higher compatibility level instance or change the compatibility level of the target database to the level of the backup.
Application compatibility issues: If you're experiencing compatibility issues with an application after changing the compatibility level, it may be because the application was designed to work with a specific compatibility level. Contact the application vendor or developer for guidance on the compatibility level to use with the application.
In general, it's important to thoroughly test any changes to the compatibility level and ensure that everything is functioning as expected before deploying to production.
Working with SQL Server compatibility levels can be complicated and requires careful testing to ensure that everything is working as expected. By understanding the differences between each level, you will be able to choose the right one for your needs and avoid any compatibility issues or query performance problems. Additionally, it’s important to keep in mind that changing a database's compatibility level is a one-way operation so it’s always best practice to back up your database before making changes. With these tips in mind, you should have all of the information needed to successfully work with different SQL Server Compatibility Levels.