![]() ![]() ![]() But in the connection, the CDM has a relatively large expansion, in addition to preserving the ER diagram of the original relationship concept, but also increased the association,inheritance two kinds of entity relationships, Let's take a look at the usage of these relationships and the difference between them (the toolbar buttons that are labeled red are used to add these relationships to the entity). Where the entity type corresponds to entity in the CDM, the attribute corresponds to the attribute of each entity in the CDM, which is basically one by one corresponding to the concept. CDM is based on the traditional ER diagram model theory, the ER diagram has three major elements: entity type, attribute and relation. CDM is the first model that most developers create when using PD, and is the abstraction at the highest level of the entire database design. ![]()
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