MIS 111 Lecture Notes - Lecture 21: Data Redundancy, Unique Key, Foreign Key

• School: University of Arizona
• Department: Management Info Systems Main
• Course: MIS 111
• Professor: ALL

Document Summary

A relational databases consists of molyihple tables that reference one another. Relational databases solves data redundancy, isolation, and inconsistency; multiple tables that reference each other. Context and meaning are added through the relationships in the database. Fields > records > tables > databases. Data with tables in it is the database, you access it through the dbms. Universities used to use ssn as sidn, now it has changed to a random sidn. Foreign key: shared field that allows relational tables to link to one another. Student example: table of students enrolled in classes -> student data -> course data -> teacher data. Primary key always uniquely identifies a record. Cascade delete messes up the entire database. Everything that is identified with one identifier record all the tables and keys in a row. Foreign key shared field that allows relational tables to link one another and minimizes data redundancy.