It teaches you about the basics and principles that are easy to miss when studying SQL. It is a great lecture. It is composed of more substantial content than the offline lecture that costs 300,000 won. (The 300,000 won lecture is my experience.) I was worried because it felt crude when I first saw the preview lecture, but I have no regrets. However, I think that those who have encountered SQL at least once will understand it better than those who are new to it. I will leave an additional comment! The instructor teaches based on MSSQL, but I took the class with MySQL. The basic principles are the same, but there are small differences in the grammar, so if you are taking the class with MySQL and you practiced according to the instructor but it doesn't work, you can just Google it! In the end, I think understanding the principles comes first, and you can memorize the grammar later.