Question
How to upgrade MS SQL Server on Plesk server to a higher version or other edition?
For example, MS SQL Server 2014 to 2017 or MS SQL Server Express Edition to Standard Edition.
Answer
It is not possible to automatically upgrade MS SQL Server via Plesk.
Check official Microsoft documentation describing how to manually perform the upgrade to MS SQL Server 2017 or Standard Edition.
For example, this article provides a checklist and steps required to do the upgrade:
Supported Version and Edition Upgrades for SQL Server 2017
And the following article provides the upgrade instructions:
The following publication may also be of help:
How to perform an SQL Server Edition Upgrade