Added a helpful resource (#8766)

* Added a helpful resource 

Hey, I've added a helpful SQL reference link in the SQL section, I think this will best add to your content and give your readers a more diverse understanding of the topic. I hope you will like this. Thank you.

* Added a useful resource 

Hey, I've added a helpful SQL reference link in the SQL section, I think this will best add to your content and give your readers a more diverse understanding of the topic. I hope you will like this. Thank you.

* Update books/free-programming-books-langs.md
Co-authored-by: NSharan J <50091666+shrn01@users.noreply.github.com>

* Update more/free-programming-cheatsheets.md

* alphabetize
Co-authored-by: NEric Hellman <eric@hellman.net>
Co-authored-by: NSharan J <50091666+shrn01@users.noreply.github.com>

books/free-programming-books-langs.md

@@ -2398,6 +2398,7 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 * [SQL For Web Nerds](http://philip.greenspun.com/sql/)
 * [SQL Notes for Professionals](http://goalkicker.com/SQLBook/) - Compiled from StackOverflow Documentation (PDF)
 * [SQL Queries Succinctly](https://www.syncfusion.com/ebooks/sql_queries_succinctly) - Nick Harrison
+* [SQL Tutorial](https://www.scaler.com/topics/sql/) - Scaler
 * [SQLite Tutorial](https://www.tutorialspoint.com/sqlite/)
 * [Use The Index, Luke!: A Guide To SQL Database Performance](http://use-the-index-luke.com)