BCS 260 Lecture Notes - Lecture 4: Multivalued Dependency, Associative Entity
Document Summary
We list attributes as part of an entity like field in our database. The example in chapter 2 was employee-degree, or employee- Another example is phone #"s, you may have one or many of them. This will be covered further when converting erds to relations later, so wanted to revisit again. Derived attributes are attributes that can be computed using the values of other attributes in the database and therefore don"t need to be stored in the database. We will discuss further at end of semester when we touch on views. Earlier we saw that relationships can connect more than two entities. Example below can be retail stores and we want to track that a customer bought an item from a specific store. Create a weak entity and connect the three participants to it with identifying relationship (depending on the business rules, more or more of these might be regular, non-identifying, relationships)
