IT 104 Lecture Notes - Lecture 8: Database Schema, Data Redundancy, Foreign Key
2 Nov 2017
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Document Summary
Database: a collection of data about a topic or topics of interest. Entity attributes: defines the information about the entity that needs to be stored. Relationship is a common item (field) between the tables. Database schema: map of the database; structure described in a formal language supported by the database management system (dbms) Dbms: a software program used to manage data in a database: The data managed by a dbms is stored in a collection of related files. Relational database: one in which data entities are related to each other. A database file or table or entity. Wasted disk space, slower processing, data inconsistency. Involves identifying individual entities within a table and dividing the file into two tables. Foreign key: connects records of different entities. Referential integrity rule: a foreign key value must always equal a primary key value. Entity integrity rule: each primary key value must be unique.
