My SharePoint 2013 was installed few years back and we never migrated or upgraded content DB from 2010 to 2013. It was a fresh installation at that time. We haven't done any SharePoint patches as well. Not sure how only few DB are showing that the upgrade not completed for few sites.
Now in SharePoint 2013 Central admin --> Upgrade and Migrations --> I sawFEW content DBs as"Database is up to date, but some sites are not completely upgraded" . Please let me know what should I do , as in TechNet https://technet.microsoft.com/en-us/library/ff607813.aspx?f=255&MSPPError=-2147217396 there are three different commands
1) Upgrade-SPContentDatabase WSS_Content1
2) Upgrade-SPContentDatabase WSS_Content -NoB2BSiteUpgrade
Santosh sethi