In the process of writing documents, there must be a system database design, so How to design the database? Let me first explain a concept to everyone:
CDM: Conceptual Data Model (CDM) is use
Tag: charge
PDM instance of computer room charging system
PDM(Physical DataModel)that is, physical data model,It details the physical realization of the database, Here we will specifically consider the details of physical implementation,including data sto