[reilly3000]

I did a MOOC on relational algebra that made me much more productive in SQL and better appreciate the gravity of what RDBMS really offer. Understanding relational algebra helps demystify the magic or query planners and grok why they both add and reduce latency based on use cases.

[edmundsauto]

Mind sharing the course? Sounds useful.

[reilly3000]

https://www.coursera.org/learn/data-manipulation

[tacotime]

here is one: https://lagunita.stanford.edu/courses/DB/RA/SelfPaced/about