SQLBolt
Learn SQL with simple, interactive exercises
https://sqlbolt.com

Simple SQL Queries
This category deals with the basics of SQL. It covers select and where clauses,
case expressions, unions, and a few other odds and ends
https://pgexercises.com

Practice SQL
An online terminal. Solve SQL query questions using a practice database.
https://www.sql-practice.com

SQL Query Interview Questions
https://www.youtube.com/playlist?list=PL2-GO-f-XvjBl5fpzdfYaPW28PwsLzLc4