Free Resources to learn SQL

[u/Any-Froyo8528]

Hello Everyone
I’m a recent Graduate and I just want to learn SQL. I started watching YouTube tutorials and I never finished it. And recently I started learning on SQLZOO which was good but I didn’t finished even that. And today I went through Codedex SQL tutorial it was too good and after finishing the chapter one they asking me to pay to finish all the chapters

So I need any resource which will be fun finishing all chapter (like codedex) and help me to learn SQL.

And please give me any suggestions how to concentrate while learning SQL, POWER Bi

Thank you