It’s not possible to downgrade a database on SQL Server. However, there are several workarounds which you can use to migrate or downgrade SQL Server 2017 database to lower version of SQL Server database. One of the most popular (and easiest) method for doing this is ‘Script entire database and all database object’.
Open Microsoft SQL Server Management Studio and connect to to the database which you want to downgrade.
Now, from Object Explorer, right click at database name and select Task, then “Generate Scripts”.
Introduction of Generate and Publish Scripts will open. Click Next Button.