Many job positions require a minimum level of SQL. The good news is that the Dplyr package in R is quite similar to SQL language, so you probably not find as difficult as a beginner would. These are some resources you might find interesting:
Learn the basics in Code Academy
Code academy platform has two courses for free that are quite popular among our students and go from a complete beginner level until intermediate
Challenge yourself at HackerRank
HackerRank focuses on competitive programming challenges, where each submission is scored on the accuracy of their output. Programmers are then ranked globally on the HackerRank leaderboard and earn badges based on their accomplishments to drive competition among users.
Create a dashboard connecting SQL queries to Grafana
SQL can also be used to build dashboard ! Grafana is a very good exemple.
Grafana is made to support multiple data sources simultaneously, through query, into one unique dashboard.
You can access your data from AWS, Google Cloud or your own server / laptop through SQL !