After listening to the previous lectures and Spring data JPA in the roadmap... I think I know why the roadmap is in this order. I really understand the reasons why it works this way and that way and why it doesn't work this way, with the contents that were explained one by one before!! Of course, there are some who are really good at development, but the order in which they teach seems to have been thought out very delicately. Thanks to that, I was able to understand the problems in the codes I've done so far, and I'm going to change them after listening to the next lecture!! Development has become fun. It's a really good lecture and a really good roadmap.