If I had been exposed to it 2 years earlier,,, Since I have been operating in the field for a long time, I was able to do the functions of small modules, but when designing the entire system DB, I was not sure because I did it by feeling. So when I was coding, I had a lot of concerns about whether the business or data structure was right or whether the data was aligned with the system. At that time, I watched more than 2 design-related books and video lectures, but I knew the theory, but when it came to designing, I had a hard time getting started. In the end, I handed over the design to someone else, but it wasn't much different. I experienced that if the DB design is weak, the service itself can be unstable. I've taken about 40% of the course, but I think I can do really well after I finish it. It's really a one-on-one tutoring. I'll try to sign up for other courses...