Potentially interesting:

https://github.com/siara-cc/sqlite_micro_logger_arduino

https://github.com/siara-cc/sqlite_micro_logger_arduino/blob...

This is a heavily subsetted implementation of SQLite3 that can read/write databases (presumably on SD cards) from very small microcontrollers.

It presumably doesn't have the same ACID compliance properties, but with a single <1.5k source file, may represent a particularly efficient way to rapidly learn the intrinsics if you happened to want to directly manipulate files on disk.

Now I'm thinking it could actually be interesting to see what drh thinks of this implementation (and any gotchas in it) because of its small size and accessibility.