Breaking changes to Database Engine features in SQL Server 2017
Applies to: 
SQL Server 2017 (14.x) and later
This article describes breaking changes in the SQL Server 2017 (14.x) Database Engine. These changes might break applications, scripts, or functionalities that are based on earlier versions of SQL Server. You might encounter these issues when you upgrade.
Breaking changes in SQL Server 2017 Database Engine
CLR uses Code Access Security (CAS) in the .NET Framework, which is no longer supported as a security boundary. A CLR assembly created with PERMISSION_SET = SAFE might be able to access external system resources, call unmanaged code, and acquire sysadmin privileges. In SQL Server 2017 (14.x) and later versions, the sp_configure option, clr strict security, enhances the security of CLR assemblies. clr strict security is enabled by default, and treats SAFE and EXTERNAL_ACCESS assemblies as if they were marked UNSAFE. The clr strict security option can be disabled for backward compatibility, but isn't recommended.
We recommend that you sign all assemblies by a certificate or asymmetric key, with a corresponding login that has been granted UNSAFE ASSEMBLY permission in the master database. SQL Server administrators can also add assemblies to a list of assemblies, which the Database Engine should trust. For more information, see sys.sp_add_trusted_assembly.
The MD2, MD4, MD5, SHA, and SHA1 algorithms are deprecated in SQL Server 2016 (13.x). Up to SQL Server 2016 (13.x), a self-signed certificate is created using SHA1. Starting with SQL Server 2017 (14.x), a self-signed certificate is created using SHA2_256.
Previous versions
- Breaking changes to Database Engine features in SQL Server 2016
- Breaking Changes to Database Engine Features in SQL Server 2014
Archived documentation for old versions of SQL Server
We accumulate and retain documentation for very old versions of Microsoft SQL Server, in sets of archived webpages. The archived webpages are not processed by search engines, such as bing.com and google.com. Yet you can see these archives at our Docs previous-versions/sql/ address:
These archives include the documentation for at least the following older versions:
- SQL Server 2014 (12.x)
- SQL Server 2012 (11.x)
- SQL Server 2008 R2 (10.50.x)
- SQL Server 2008 (10.0.x)
- SQL Server 2005 (9.x)
SQL Server 2014 documentation is still available on our main Docs address.
SQL Server 2022 documentation is available on our main Docs address. Then, you can use the versioning dropdown near the top of the page, to select another version of interest.
For more information about the documentation for previous versions of SQL Server, see Previous versions of SQL Server documentation.