Use cartesian products to solve a practical problem

The nhib.pdf used in the project is less efficient when it encounters some problems. Here we have a practical scenario and solved this problem using cartesian products. I recently read about ORM from maintin flower'sArticleOrmhate also gave me a deeper understanding of ORM. In this example, we can see that ORM does not mean that we do not need to know the database or the underlying knowledge of the database, it is not omnipotent, so the underlying knowledge of the database is very important, and ourProgramData cannot be separated. Data often involves the participation of databases. We can imagine how important the bottom layer of the database knows to us. Read the full text