One Drive, Drop Box, Mega? Those aren't database services—Google Drive isn't either—anyway they're cloud storage platforms. Databases refer to something else.
I think he meant data base as is a base that stores data. Without realizing database is actually a technical term...
if you want online storage the best deal is mega.nz 50gb free, but if you talk about running some type of SQL database , then you're paying for it but it's easy as hell to do that on your own pc for free then use mega to back the .db file on it via the free sync app, but your question is way to open ended