Data Science & Analytics

Select Star

• For beginners
• Little background coding needed

W3schools.com

• For beginners
• Information about SQL starting from the beginning with embedded practive problems

Code Academy

• Free basic account
• Search for different courses including Learn SQL

Leetcode

• Practice problems using SQL

SQL Bolt

• Tutorials with interactive exercises

HackerRank

• Practice problems using SQL

SQL Interview Questions  

• Medium-Hard SQL questions

Paid resounces 

LinkedIn

• Video lessons on SQL
• Requires LinkedIn premium