I completed the course of “The complete SQL Bootcamp” via Udemy. In this course, I used PostgreSQL, and learn everything about SQL. I suppose, in any kind of business field, I should have the opportunity to use SQL. Also, now I am studying how to make web application(Ruby and Rails), from this perspective, to learn about database is really helpful. I would like to make use of this knowledge for making web app. This course is quite good for learning SQL!!!