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