Entitiy Relationship Introduction Diagram

Data Modeling for
Database Design 1

Part # 2
2
Study Objectives
 Understand concepts of data modeling and its
purpose
 Learn how relationships between entities are
defined and refined, and how such relationships
are incorporated into the database design
process
 Learn how ERD components affect database
design and implementation
 Learn how to interpret the modeling symbols

Part # 2
Data Model
 Model: an abstraction of a real-world
object or event
 Useful in understanding complexities of the
real-world environment
 Data model
 A diagram that displays a set of tables and
the relationships between them
 Next Slide: “Restaurant” Access data model
using Entity Relationship Diagram (ERD)

Part # 2
Access Data Model using ERD
4

Part # 2
What is an Entity Relationship
Diagram (ERD)?
 ERD is a data modeling technique used in
software engineering to produce a
conceptual data model of an information
system.
 So, ERDs illustrate the logical structure of
databases.
 ERD development using a CASE tool
 Powerdesigner by SAP

Data Modeler by Orcale
5

Part # 2
The Importance of Data Model
 Blue print: official documentation

Blue print of house
 Employee’s w/o DB knowledge can understand

a data model diagram vs. a list of tables

Used as an effective Communication Tool

Improve interaction among the managers, the
designers, and the end users
 Independence from a particular DBMS

Network DB, Object-oriented DB, etc.

Part # 2
7
 The data modeling revolves around
discovering and analyzing organizational
and users data requirements.
 Requirements based on policies, meetings,
procedures, system specifications, etc.
 Identify what data is important
 Identify what data should be maintained
Data Model (con’t)

Part # 2
8
 The major activity of this phase is identifying
entities, attributes, and their relationships to
construct model using the Entity Relationship
Diagram.
 Entity  table
 Attribute  column
 Relationship  line
 Basics of Data Modeling Video
 Until business rules # 3 (9:20)
ERD

Part # 2
9
How to find entities?
 Entity:
 "...anything (people, places, objects, events, etc.)
about which we store information (e.g. supplier,
machine tool, employee, utility pole, airline seat,
etc.).”
 Tangible: customer, product
 Intangible: order, accounting receivable
 Look for singular nouns (beginner)
 BUT a proper noun is not a good candidate….

Part # 2
10
Entity Instance
Entity instance: a single occurrence of an entity.
 6 instances
Student
ID
Last
Name
First
Name
2144 Arnold Betty
3122 Taylor John
3843 Simmons Lisa
9844 Macy Bill
2837 Leath Heather
2293 Wrench Tim
Entity: student
instance

Entitiy Relationship Introduction Diagram

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