Which {SQL,} databases do this as a native, online database feature; so you don't have to pull backups to sqldiff?

E.g. django-reversion and VDM do versioned domain model on top of SQL, but not with native temporal database features.

Many apps probably could or should be written as mostly-append-only - not necessarily blocking until the previous record is available to hash – but very few apps are written that way, so run sqldiff offline.