Chapter 6: Databases and Information Management

Bit, Byte, Field, Record, File, Database

Data Hierarchy (Ascending)

8:1

Bits to Byte Ratio

Database

Collection of related files containing records on people, places, or things

Entity

Generalized category representing a person, place, or thing on which we store and maintain information

Attributes

Specific characteristics of each entity

Fields

Aka columns, store data representing an attribute

Records

Aka rows, store data for separate records, or tuples

Key Field

Uniquely identifies each record

Primary Key

One field in each table that cannot be duplicated and provides an unique identifier for all information in each row

One-to-One Relationship

A single record in Database A is ONLY related to a single record in Database B (and vice versa)

One-to-Many Relationship

A single record in Database A is related to multiple records in Database B, but a single record in Database B is only related to one record in Database A

Many-to-Many Relationship

Requires a “join table” or intersection relation that links to two table to join information

Example of a One-to-One Relationship (1)

The relationship between an employee and their parking spot

Example of a One-to-One Relationship (2)

The relationship between a student and their student ID number

Example of a One-to-Many Relationship (1)

The relationship between a student and their shared dorm

Example of a One-to-Many Relationship (2)

The relationship between a plane ticket and its corresponding flight number

Example of a Many-to-Many Relationship (2)

The relationship between students and classes (class registrations)

Example of a Many-to-Many Relationship (1)

The relationship between employees and their shifts

Bit

The bottom of the data hierarchy, representing either a 0 or a 1

Examples of Entities

SUPPIER, PART, CUSTOMER, SALES

Examples of Attributes

SUPPLIER name, address

PART description, unit price, supplier

Foreign Key

A field in one table that uniquely identifies a row of another table

Referential Integrity Rules

Used by relational databases to ensure that relationships between coupled tables remain consistent.