SQL
–SQLZoo.net
–Tutorials Point
–RIP Tutorial (Also good for Python Reference)

Python
–DataCamp.com Free Tier/ Tutorials
–Kaggle.com
–Full Stack Python 
–Stack Overflow  (Be specific when phrasing your search! Copy your error message!)

Database/ Data Engineering Knowledge 
–Database System Concepts Book Online
–Oracle.com
–Databricks.com (Great resource for Delta Lake Architecture)

Azure (Fundamentals, Data Engineering, DevOps)
–Microsoft Learn
–Whizlabs.com (offers 1 free exam per certification path)
–John Savill’s Technical Training