AFM341 Lecture Notes - Lecture 12: Unique Key, Referential Integrity, Foreign Key
28 Jun 2018
School
Department
Course
Professor
Contains info for objects, events, people, places.
â—‹
Three types of models are used today
â—‹
A
database
is a collection of related data for various uses.
•
Used in mainframe database management systems
â—‹
e.g. asset
--
> current/non
-
current asset
--
> cash/AR/inventory

Organize data into tree
-
like structure with parents/child
â—‹
Data elements are 1:N mapping (one to many relationships)
â—‹
Hierarchical data models
•
Many to many relationship.
â—‹
Lattice structure (looking like a big net) connecting parent and child records together
â—‹
Network data model
is a flexible model representing objects and their relationships
•
Identify relationships at the time the database is created or much later whenever new
information requirements from the data model are desired.
â—‹
Unlike the first two data models, relational data model can be made up as needed
â—‹
Relational data model
stores information in the form of related two
-
dimensional tables
•
As business and informational requirements change, handle changes quickly and
easily

Flexibility and scalability
â—‹
Easy to communicate to database users and database developers

Simplicity
â—‹
Requires each piece of data to be recorded only in one place.

Helps keep the information updated because the information only has to be updated
once in one database

Reduced information redundancy
â—‹
Relational data model is more preferred because:
•
Introduction
Designed to manage a database's storage and retrieval of information
â—‹
Database management system (DBMS)
-
defined as a computer program that creates, modifies,
and queries the database.
•
Data dictionary
-
describes the data fields in each database record such as field description, field
length, field type
•
Data administrator
-
the database administrator is responsible for the design, implementation,
repair, and security of a firm's database.
•
Definitions for databases
Fundamentals of relational databases
Entity = class, could be a person, place, thing, transaction
•
Classes could be grouped into resources ( R ), events ( E ), and agents ( A ) in data modeling
•
Resources are those with economic value to a firm e.g. cash
•
Events are the various business activities conducted in daily operations such as sales
•
Agents are the people such as customers
•
Attribute for customer e.g. customer ID, customer last name, address
â—‹
Attribute for sales could be invoice number, customer ID, date, product number
â—‹
Attributes for product may include product number, product name, and product price
â—‹
Attributes
are characteristics, properties, or adjectives that describe each class.
•
Table represents class or a relationship among classes with rows and columns like a
spreadsheet.
â—‹
The columns in a table are called fields and represent the attributes of the classâ—‹
The rows in a table are called
records
â—‹
Three main constructs in a relational database: tables, attributes, and records
•
Entities and attributes
A
PK
is an attribute or combination of attributes that uniquely identifies a specific row in a table
•
Keys and relationships
Chapter 4
-
Relational Database and Enterprise Systems
January 10, 2018 1:38 PM
AFM 341 Page 1
Document Summary
Chapter 4 - relational database and enterprise systems. A database is a collection of related data for various uses. Organize data into tree-like structure with parents/child e. g. asset --> current/non-current asset --> cash/ar/inventory. Data elements are 1:n mapping (one to many relationships) Network data model is a flexible model representing objects and their relationships. Lattice structure (looking like a big net) connecting parent and child records together. Relational data model stores information in the form of related two-dimensional tables. Identify relationships at the time the database is created or much later whenever new information requirements from the data model are desired. Unlike the first two data models, relational data model can be made up as needed. As business and informational requirements change, handle changes quickly and easily. Easy to communicate to database users and database developers. Requires each piece of data to be recorded only in one place.
