Lecture10DiscussionQ

Lecture10DiscussionQ - Exercise 15.1: Give an algorithm to...

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Exercise 15.1: Give an algorithm to convert a relational schema to an entity- relationship one (Challenging Problem!). Let’s use the following sample database to illustrate the algorithm steps: student (StudentID , FirstName, LastName, StreetAddress) class (ClassID , description, InstrictorID) enrollement (ClassID , StudentID , grade) Instructor (InstructorID , FirstName, LastName) 1. Find the relations that don’t have foreign keys. Those relations convert directly to the entity types. Student and instructor entities don’t have foreign keys. 2. Identify the relationship types. Those relations have two or more foreign keys, and the primary key is composed of those foreign keys. In our case, enrollment is a relationship type with the grade attribute. 3. The rest of the relationships are entity types. Add them and their attributes to a model. In our case, we don’t have any more relationships to add. We just add the attributes to the class entity. Student
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Lecture10DiscussionQ - Exercise 15.1: Give an algorithm to...

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