I finished up to DB Part 1. Since it was something I had seen once at the boot camp, I studied it as if I was studying it again. At the camp, the transaction part was passed over, but it was a lecture that made me realize that this was the mechanism because it was covered in detail. I learned quite a bit, but DB Part 2, JPA, Advanced, Spring Boot... I still have a long way to go. I will listen diligently.