Hello, I'm @dakeshi's supervisor!
Sometimes, even though we don't want it to happen, low quality tutorials or tutorials of generally low value get approved for vastly different reasons. While this tutorial may be a great tool for someone to start with PostgreSQL, there's a lot of tutorials you can access by using external resources, like google & youtube, which means that this tutorial is not of great value to the project.
Thank you for your understanding and I hope you can contribute some more advanced PostgreSQL tutorials to us!
Thank you very much for your answer. I'm more calm :). I can contact you to receive some observations of future tutorials that I want to do please