OpenVMS', BeOS', IBM's ISAM's, and Reliant Nitro'sfilesystems were database-like:
http://neilrieck.net/docs/openvms_notes_rms_rdb.html
https://en.m.wikipedia.org/wiki/Be_File_System
http://neilrieck.net/docs/openvms_notes_rms_rdb.html
https://en.m.wikipedia.org/wiki/Be_File_System