It should be understood that there is no discrete mathematics in the part of relational algebra, that is, division is difficult, and subsequent SQL statements have nothing to do with discretization. Exist in SQL refers to discrete things, but it does not affect learning. However, the later part of relational theory needs the foundation of discrete mathematics, otherwise it is difficult to understand.

If you don't have to learn discretization from the perspective of database use, it's better to learn about it when you take the postgraduate entrance examination.