Making an E/RD:

When to Use Designer;When to Use Your Brain

A presentation on using Oracle Designer to create anEntity/Relationship Diagram

for a useful database.

Mike Moxcey:

• Programmed in Oracle for 14 Years.– Built forms in Oracle 4 and 5 – Used ReportWriter 1.0 and 1.1 – Heavy experience in SQL, SQL*Plus

and DBA – Built Web Sites with Perl and Oracle

I work for the President: George Bush

• White House – US Department of Agriculture

•Animal and Plant Health Inspection Services

– Wildlife Services » Operations Support Staff

Management Informations Systems

Me

Both of us are often called by

    our middle initial: • He's W

– (because of his Dad)

• I'm S – (because of another guy at work

named Mike)

Programmer for Wildlife Services

• Providing Support for Existing Oracle 7 System

• Building Completely New System in Oracle Designer

Worked in the Same Overall Agency

– APHIS: IT• Plant Protection and Quarantine • Veterinary Services• Wildlife Services

Not a consultant who leaves

Overview: 3 Parts to this Talk

• Why Use Users?• How to Use Users• How to Use Designer

– Making an E/RD– Generating Prototype Forms

Why Use Users?

• You're supposed to• All the mgmt books say so• It's good karma

Definition: A successful system is one that is

used.

• Not one that works correctly• Not one with an elegant design• Not one that's finished

Everyone Hates Data Entry

• Data is good for managers. • Workers just want to do their

job.• Painful to enter pointless data • Less painful for useful data

Best Data Entry Is Part of Job

– Grocery Store Scanners– Time Cards– Keystroke Counters

• Can design without users – (You have management buy-in)

Most Data Is Entered after

the Job Is Done• Estimate how long it took• Write down your mileage• I'm focused on next task

Good Data Requires User Buy-In

• Imagine the Dilbert boss wants a DBS for programmer time

– Hours/form or procedure – Lines of form code

• What would you want to measure? – Form size, procedure complexity

• What could you measure well? – Time, lines of code, speed of

procedure

• What can't be measured? – Elegance, maintainability

Get the Users to Design Their System

• You're the Architect; Not the Client

• You're the Builder; Not the Buyer

If Management Isn't Behind the System

Put the System Behind You

– Slam it out and move on

Get a Variety of Users Get Good Users

– Don't accept "Spares" – Make management assign the workers

• Otherwise forego the group and work one on one

Get a Time Commitment

• Need to train the users • Need to forge relationships • Need to build trust

Teaching Database Designto Users

• Tables are like a spreadsheet without any repeated data

• Data integrity is critical• Links between tables make the

database work

Know the Modeling Concepts

• Entities • Relationships• Foreign Keys

– The Data Model Resource Book by Silverston, Inmon, and Graziano

Brainstorm on Entities

• Entities will become tables – (don't explain why "Account" won't

exist)

• Entities are nouns: – person, place, thing, event, or concept

Consolidate Ideas and Terms

• Listen! Don't talk. • Hear what's important and why.• Take notes!

• Create list of Candidate Entities •Some Nouns Are Attributes Now

Teach Relationships In-depth

• Demonstrate Foreign Keys

Two Parts to Relationships

• Optional vs. Mandatory • One vs. Many

Show Foreign Keys

• Employee Table– ID– NAME

Emp Records1 George2 Nancy3 Lestat

• Job Table– ID– NAME– FKEY

Job Records1 Combine 22 Stir 13 Serve 24 Consume 3

Ask Questions

Songs and Authors Entities

• Optionality– Must a Song have an Author?– Must an Author have a Song?

• Cardinality– Can an Author write more than one

Song?– Can a Song have more than one Author?

Draw Relationships

• Discuss and verify them

• Make Associative Entities– This is a tricky concept for users.– Explain it well.

• Explain why the Account" entity won't exist

• Argue about Intelligent Keys

Show Associative Entities

Songs and Authors Example

Song Song_Author AuthorName ID NameID……………………SONG_ID HistoryHistory AUTHOR_ID……ID

Using Oracle Designer

• Repository Must Be Installed • Requires an Account

•Open Designer – Open the Entity Relationship

Diagrammer – Make Work Areas and Containers – Name the Diagram: ERD_*

Add Entities

• Name • Short Name = Prefix • Plural = Table Name

Create Relationships

1. Choose correct type 2. Click on From Entity 3. Click on To Entity 4. Name the Relationship

Make Diagram Readable

• Put in about 20 Entities • Group by Subject Area

This Should Work • Try Select All and AutoLayout • Arrange/Resize Entities

Better-Looking Diagram

1. Select Relationship 2. Choose Edit; Select Same Type 3. Click Autolayout

Domains

• Use E/R Diagrammer or RON – Enter Name, – Datatype, and – Maximum Col Length

Enter Attributes

• Can be done as you do Entities

Entity;Properties has many tabs– Attributes: Name, Optional, Primary– Att Detail: Apply domains

Checking the Design

• Run Scenarios – (capture info during meetings)

• Use Reports for Users– Open Repository Reports – Entity/Relationship Modelling:

8 different reports • Use the Previewer, not the Parameters

Alternate Reports

• Perl to strip/reformat • Open .rdf in Developer • Write own SQL scripts

Fine-tune diagram

**Don't need users

• Drop weak entities • Look for common data • Look for unneeded data

Categories

• These are how users organize data • They drive the reports • Verify groupings with users

Categorization Questions:

• Can it only ever be one kind? – Apple or Pear

• Are there subkinds? – MacIntosh or Red Delicious

• Are there different kinds of kinds? – Apple is Red, is Fruit, is Round

More Categorization Questions:

• Can it change kinds over time? – Can an Apple become a Pie?

• Can it be multiple similar kinds at once? – Piano is both String and Percussion – Trees: Natural Resource, Landscaping,

Silviculture

Set up Types (can only be one)

• Set up Classes, Categories, etc. • Set up Hierarchies

Sorting Data is aJob for Users

• This group needs to be permanent • They are your data librarians

Building the System

• We know we want a database • Don't need Process Modeller • Don't need Dataflow Diagrammer

Function Hierarchy Diagrammer

• Make a Function for every form • Assign Entity Usages• Run Utilities; Function/Attribute

Matrix to assign IRUN for attributes

Create Tables

• Run Database Design Transformer

• Design Editor: run Generate; Generate Database from Server Model

• SQL: Execute the Table Creation scripts

Create Candidate Modules

• Transform Preliminary Designs: Application Design Transformer – Select top function

• Design Editor – Modules Tab – Modules are Named, Numbered – Rename and Uncandidate Them

• (Properties; Candidate? = No)

To Regenerate

• Design Editor: Delete Unneeded Modules

• Design Editor: Delete Table defs (views, seqs, etc.)

• SQL: Drop Tables and Sequences (by script or by user)

Take Small Steps

• Make a Test Work Area • Create Tiny Modules • Read the Help screens

Oracle Designer is a complex tool

System design is a complex process

• Use Organization's collective brain power for a good system.

• More info at home.att.net/~mike.moxcey/pgm/

www.aphis.usda.gov/~mmoxcey/