dagger VS sqlite

I learned a ton about Java and pragmatic algorithm development from reading Dagger (https://github.com/square/dagger) and porting it to C#. It's small enough that you can grok it in a reasonable amount of time, but sophisticated enough that there's a lot to learn. (Yes it's deprecated in favor of Dagger 2, but the latter is a tougher slog IMO)

Actually most of the big Square OSS libraries are great to read - okio, okhttp, picasso.

SQL (Structured Query Language) databases are relational databases. They organize data into tables with rows and columns, and they use SQL for querying and managing data. Examples include MySQL, PostgreSQL, and SQLite.

SQLite: A lightweight, self-contained SQL database, best for standalone applications, embedded systems, or small-scale applications not requiring a client/server DBMS.

FerretDB is an open source document database that adds MongoDB compatibility to other database backends, such as Postgres and SQLite. By using FerretDB, developers can access familiar MongoDB features and tools using the same syntax and commands for many of their use cases.

Rust stdlib code is quite high quality although not particularly dense due to large amount of comments. Start from the docs, and click any source link: https://doc.rust-lang.org/std/vec/struct.Vec.html

Sqlite is supposedly high quality C code: https://github.com/smparkes/sqlite

For videos of someone (Casey Muratori) writing video game code and debugging it, Handmade Hero: https://handmadehero.org/

A blog post about how to write code by the same author: https://caseymuratori.com/blog_0015

For how to implement a fairly advanced type system, Typing Haskell in Haskell: https://gist.github.com/chrisdone/0075a16b32bfd4f62b7b

But, honestly, you're probably better off writing code yourself and learning by doing.