Going to take a SQL class next week (after not touching it for over a decade), and I decided to get started early. Finding decent starter tutorials that don’t begin with the assumption you are either completely clueless or somehow a veteran choosing to just now start a tutorial was difficult.
Two great sites that have helped my rusty mind, a great tutorials is found at https://www.w3schools.com/sql/default.asp and a nice online sandbox is https://www.tutorialspoint.com/execute_sql_online.php. They are both extremely useful, but it took awhile to find a good sandbox. It certainly feels odd going from teacher to student, but should be interesting.