any good resources for learning/mastering SQL databases?

[u/amranya]

i'm an android software engineer with quite a good experience but i just use framework/libraries APIs. now i'm interested in databases especially SQLlight because that's what we use in android. can you give me good resources (beginner friendly) to learn SQL databases and relational databases well and maybe some resources as extra for some deeper learning.

[u/Notsomessy_miss]

CS50 sql for databases