MIS 111 Lecture Notes - Lecture 16: Peter Chen, Hard Disk Drive, Foreign Key
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Document Summary
Database as a real-world model: a database can be used to capture real-world relationships between people. Facebook, as an example, is a database that allows you to see information related to your friends and their connections with one another. Data modeling: entity relationship (er) diagram as a model of data and relationships. In 1976, peter chen from louisiana state university developed a very effective way of conceptualizing data. What does an er diagram tell us: actors in the design (entities, relationships among actors (links) Entities and entity classes: entity - a specific person, place, thing, or event about which information is maintained, students, entity class - an abstract representation of all attributes of a particular type of entity. Attributes: attribute - a characteristic or quality of a particular entity class. Students: student id, student name, student email. Relationships and constraints: relationships connect entitites, students - enroll - courses, constraints define business rules.