conceptual database design

Muhammad Umair

Conceptual Database Design

Oracle Database 11g Developer Track

Why do you need a database?

› To solve a problem– You have some data(information) of your client or your business you

want to create.– There must be must be some data you want to store– And this data could be anything about customers, employee, products,

dates, numeric from, document fine, images, audio/video etc.› But you can already store data

– Write in a text file and type in your information– Use spreadsheet– If you got documents organize them in folder

Why do you need a database?

› Many small business starts with spreadsheet– And work continue like this for years– And that might be causing no problem

› Just having data is not good enough reason to have database– Having data is not the problem

Why do you need a database?

Why do you need a database?

› Problems– Size– Ease of update– Accuracy– Security– Redundancy– Importance

Why do you need a database?› Size

Why do you need a database?› Ease of update

Why do you need a database?› Accuracy

Why do you need a database?›Security

Why do you need a database?›Redundancy

Why do you need a database?›Importance

Why do you need a database?

› You might have all of these problems or some of these problems

› These are the reason we need database› These are the problems

Building an Application with a DBMS

› Requirements modeling (conceptual, pictures)– Decide what entities – should be part of the application – and how they should be linked.

Database Design Process› Conceptual Model

– Merge the collective needs of all applications– Determine what Entities are being used

› Some object about which information is to maintained– What are the Attributes of those entities?

› Properties or characteristics of the entity› What attributes uniquely identify the entity

– What are the Relationships between entities› How the entities interact with each other?

Entities

Attributes

Relationships between entities

Product

address

buys

Database Design Process

Database Design Process› Logical Model

– How is each entity and relationship represented in the Data Model of the DBMS› Hierarchic?› Network?› Relational?› Object-Oriented?

› Determine user requirements› Determine business rules› Build conceptual data model

– outcome is an entity-relationship diagram or similar communicationtool

Conceptual Database Modeling

EnterpriseModeling

ConceptualData Modeling

LogicalDB Design

Physical DBDesign/Creation

DBImplementation

DBMaintenance

Build Conceptual Data› To build a conceptual data model of data requirements of enterprise– Model comprises entity types, relationship

types, attributes and attribute domains, primary and alternate keys, and integrity constraints

› Step 1 Identify entity types– To identify required entity types– Typically nouns, noun phrases, major

objects

Extract from data dictionary for Staff user views of Dream Home showing description of entities

Build Conceptual Data

› Step 2 Identify relationship types– To identify important relationships that

exist between entity types– Typically verbs, verb phrases– Determine multiplicity constraints

Extract from data dictionary for Staff user views of Dream Home showing description of relationships

First-cut ER diagram for Staff user views of Dream Home

Build Conceptual Data› Step 3 Identify and associate attributes with entity or relationship types– To associate attributes with appropriate

entity or relationship types and document details of each attribute

– Determine information required › Step 4 Determine attribute domains

– To determine domains for attributes in data model and document details of each domain

Extract from data dictionary for Staff user views of Dream Home showing description of attributes

Step 1 Build Conceptual Data› Step 5 Determine candidate, primary, and alternate key attributes– To identify candidate key(s) for each entity

and if there is more than one candidate key, to choose one to be primary key and others as alternate keys

– Strong entity› Primary key easily identifiable

– Weak entity› Primary key not identifiable› Need to map entity & relationship to owner entity to

identify primary key

ER diagram for Staff user views of Dream Home with primary keys added

Build Conceptual Data

› Step 6 Consider use of enhanced modeling concepts (optional step) – To consider use of enhanced modeling concepts,

such as specialization / generalization, aggregation

Build Conceptual Data

Build Conceptual Data Model

› Check model for redundancy – To check for presence of any redundancy in

model and to remove any that does exist

Example of removing a redundant relationship called Rents

Example of a non-redundant relationship Father Of (Time dimension example)

Build Conceptual Data Model› Step 8 Validate conceptual model

against user transactions – To ensure that conceptual model supports

required transactions› Describe transactions› Use transaction pathways

› Example– List the details of properties managed by a

named member of staff at the branch

Build Conceptual Data Model

› Step 9 Review conceptual data model with user– To review conceptual data model with user

to ensure that model is ‘true’ representation of data requirements of enterprise