For absolute basics to advanced SQL tutorials & interview preparation : https://www.udemy.com/course/practical-sql-masterclass-with-mysql/?couponCode=MYSQL2020JUNE16
Also visit MongoDB and Python courses :
Learn MongoDB : https://www.udemy.com/course/mongodb-in-nutshell-example-driven-quick-start-in-mongodb/?couponCode=MONGO2022JULY
Learn Python : https://www.udemy.com/course/python-for-those-absolute-beginners-who-never-programmed/?couponCode=PYTHON2022JULY
