Here are a few amazing resources to develop coding skills in various programming languages:
https://lagunita.stanford.edu/courses/DB/2014/SelfPaced/about
https://www.sqlteaching.com/
http://www.freecodecamp.com/
http://www.learncpp.com/
https://lagunita.stanford.edu/courses/DB/2014/SelfPaced/about
https://www.sqlteaching.com/
http://www.freecodecamp.com/
http://www.learncpp.com/
