For me it was quite confusing to find the 2017 version of LocalDB and it is not a streamline process to upgrade your local default instance. The link for “SQL Server 2017 Express LocalDB” on official website (https://www.microsoft.com/en-us/sql-server/sql-server-editions-express) leads to “SQLServer2016-SSEI-Expr.exe” which runs a SQL Server 2016 with SP2 installer. Now what?

The easiest way to upgrade your LocalDB instance to 2017 is:

1. Download the LocalDB 2017 installer directly:
   https://download.microsoft.com/download/E/F/2/EF23C21D-7860-4F05-88CE-39AA114B014B/SqlLocalDB.msi
2. Before running the installer, delete your current MSSQLLocalDB instance:

   sqllocaldb stop MSSQLLocalDB
   sqllocaldb delete MSSQLLocalDB
   

3. Run the LocalDB 2017 installer. It will create a new MSSQLLocalDB instance.
4. [OPTIONAL] If you did not delete the older instance before running the installer, you can delete it now and recreate the instance. It will be created as new version:

   sqllocaldb stop MSSQLLocalDB
   sqllocaldb delete MSSQLLocalDB
   sqllocaldb create MSSQLLocalDB
   

5. Now you can re-attach your original databases using SQL Server Management Studio (RClick + Attach…)
6. Done.

Credits:

• https://stackoverflow.com/questions/42951632/sql-server-express-localdb-msi-offline-installer/42952186#42952186
• Miroslav Louma, HAVIT