Easy, flexible learning to pop into for short periods at a time. Also servers as useful refresher or check on code and fixing errors.

Took python intro, but loads of other really good courses. Really good way to learn in an interactive and hands on way

Really useful online book that's accessible to those relatively new to R. Teaches you skills that can be easily applied to most coding projects so has actually helped me do my job better. You can work through the whole thing in order to get a detailed overview of data science in R, or just dip into relevant chapters when you have a specific issue to solve. I particularly like that there are exercises throughout the book so you can put what you've read about into practice and really solidify lear

https://www.w3schools.com/sql/ A really good, easy to use course covering the basics of SQL. This will teach you all you need to know to get going querying data and merging tables, and prepare you for more advanced work. I still use it occasionally and also recommend it in SQL courses I teach.