Update README.md

Author: learning-zone

README.md

@@ -9,6 +9,7 @@
 * [HTML5 Interview Questions](https://github.com/learning-zone/html-interview-questions)
 * [CSS Interview Questions](https://github.com/learning-zone/css-interview-questions)
 * [JavaScript Interview Questions](https://github.com/learning-zone/javascript-interview-questions)
+* [SQL Interview Questions](https://github.com/learning-zone/sql-interview-questions)
 * [Node.js APIs](nodejs-api.md)
 * [Node.js Coding Practice](nodejs-programming.md)
 * [Node.js Commands](nodejs-commands.md)