gama ilp course ware sdlc data base design new

8/6/2019 GAMA ILP Course Ware SDLC Data Base Design New

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Data Base Design

UST Global

120 Vantis AlisoViejo CA 92656Phone: (949) 716-8757www.ust-global.com


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Concepts of Database Designing

Database Designing is the process of convertingSystem Requirements to a database model.

A typical database design lifecycle constitutes thefollowing

1. Conceptual Modeling Data Flow Diagrams

2. Logical Modeling ER Diagrams

Data Dictionary

Normalization First NF

Second NF

Third NF


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Concepts of Database Designing Contd..

3.Physical Database Design Storage Designing

Logical Storage

Physical Storage

Data Flow Design

Data Integrity Referential Integrity

Rules and Constraints


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To document the business informationrequirements

To identify reuse requirements andopportunities

To document data requirements basedfunctional activity and/or business rules

To assist in identification of redundantprocesses

To guide and support consistent dataadministration

Purpose of Database Modeling


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Logical Designing

Any system has or should satisfy a fewimportant characteristics. They are: A well defined system boundary

A well defined set of inputs and outputs

A data store that stores information

Logical Designing is the process of creatingthe logical architecture of a system. Thelogical architecture comprises of defining thelogical components that influence the

system like processes, data flow, entities etc.


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Logical Designing Contd..

Following are the various approaches thatare being used as part of the designingprocess. Data Flow Diagrams

Entity Relationship Diagrams

Data Dictionary

Decision Tables and Decision Trees

State Transition Diagrams


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Entity Relationship Diagrams (ERD)

While Data Flow Diagrams show the

flow of data between processes, Entity

Relationship diagrams show the

relationship between data. An ER diagram is an effective tool to

demonstrate and document the data

relationships which helps bettermanagement and maintenance of data.

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ERD

Attribute An Attribute is a property that explainsan entity.

Relationship A Relationship is a definition on theassociation or interaction between Entities

We can classify Relationships according to twocharacteristics

Optionality

Mandatory Relationship

Optional Relationship

Cardinality One-to-One

One-to-Many

Many-to-Many

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ERD - Notation

Data Element

Relationship

Associated Object

Cardinality Exactly one

Cardinality Zero or one

Cardinality Mandatory Many

Cardinality Optional Many


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Developing an ERD

Developing an ERD requires an

understanding of the system and its

components.


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How do we start an ERD?

1. Define Entities: these are usually nouns

used in descriptions of the system, in the

discussion of business rules, or in

documentation; identified in the narrative2. Define Relationships: these are usually

verbs used in descriptions of the system or

in discussion of the business rules (entity

______ entity); identified in the narrative


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How do we start an ERD? Contd..

3. Add attributes to the relations; these are

determined by the queries, and may also

suggest new entities, e.g. grade; or they

may suggest the need for keys or identifiers4. Add cardinality to the relations; Many-to-

Many must be resolved to two One-to-Many

using an additional entity. Usually

automatically happens. Sometimes involvesintroduction of a link entity (which will be all

foreign key) Examples: Patient-Drug


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How do we start an ERD? Contd..

5. This flexibility allows us to consider a variety

of questions such as:

Which beds are free?

Which assistants work forDr. X?

What is the least expensive prescription?

How many doctors are there in the

hospital? Which patients are family related?

6. Represent that information with symbols


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ER Diagram Examples

In a company, each division is managed by only one manager and eachmanager manages only one division

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In a college, every student takes as many courses and every course is taken bymany students

Among the mobile manufacturing companies, a company manufactures manycars, but a given car is manufactured in only one company


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Data Dictionary

A Data Dictionary is an organized documentation ofData Elements, Data Structures and Data Flows.

Data Element - Piece of data, which cannot bedecomposed further in the current context of the

system. Examples are purchase_order_no,employee_name, interest_rate, etc.

Data Structure - Composed of data elements or otherdata structures. Examples are Customer_details,which may be composed ofCustomer_name and

Customer_address. Data Flow is composed of data structures and/or

data elements. Definitions of dependent datastructures/data elements precede the definition ofdata flow. While defining the data flow the

connecting points should be mentioned.16


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Transition from Logical to Physical

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Logical Physical

Data Entities Tables

Attributes Columns/Fields

Entity Instances Rows/Records

Relationships/Cardinality Primary/Foreign Keys


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Database Normalization

Database Normalization is the process of efficiently organizing data to achievethe following goals

Avoid data redundancy

Ensure data integrity.

There are multiple levels of normalization. A typical application databaseshould be ideally at the 3rd normal form

First Normal Form

A relation R is in first normal form (1NF) if and only if all underlyingdomains contain atomic values only.

Remove redundant columns

Primary Key

Second Normal Form

A relation R is in second normal form (2NF) if and only if it is in 1NF and

every nonkey attribute is fully dependent on the primary key. Enforce primary key-foreign key relationship

Third Normal Form

A relation R is in third normal form (3NF) if and only if it is in 2NF and everynonkey attribute is nontransitively dependent on the primary key.

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First Normal Form (1NF)

There are no repeating or duplicate

fields.

Each cell contains only a single value.

Each record is unique.

Identified by primary key

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Example

Table is not in first normal form

because:

Multiple items in color field

Duplicate records / no primary key

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Item Colors Price Tax

T-shirt Red, blue 12.00 0.60

Polo Red, yellow 12.00 0.60

T-shirt Red, blue 12.00 0.60

Sweatshirt Blue, black 25.00 1.25


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Example

Item Color Price Tax

T-shirt Red 12.00 0.60

T-shirt Blue 12.00 0.60

Polo Red 12.00 0.60

Polo Yellow 12.00 0.60Sweatshirt Blue 25.00 1.25

Sweatshirt Black 25.00 1.25

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Table is now in first normal form


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Second Normal Form (2NF)

All non-key fields depend on all

components of the primary key.

Guaranteed when primary key is a single

field.

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Example

Item Color Price Tax

T-shirt Red 12.00 0.60

T-shirt Blue 12.00 0.60

Polo Red 12.00 0.60

Polo Yellow 12.00 0.60Sweatshirt Blue 25.00 1.25

Sweatshirt Black 25.00 1.25

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Table is not in second normal formbecause

Price and Tax depend on item, but not

color


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Example

Item Color

T-shirt Red

T-shirt Blue

Polo Red

Polo YellowSweatshirt Blue

Sweatshirt Black

Item Price Tax

T-shirt 12.00 0.60

Polo 12.00 0.60

Sweatshirt 25.00 1.25

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Tables are now in second normal form


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Third Normal Form (3NF)

No non-key field depends upon

another.

All non-key fields depend only on the

primary key.

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Example

Item Color

T-shirt Red

T-shirt Blue

Polo Red

Polo YellowSweatshirt Blue

Sweatshirt Black

Item Price Tax

T-shirt 12.00 0.60

Polo 12.00 0.60

Sweatshirt 25.00 1.25

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Tables are not in third normal formbecause

Tax depends on price, not item


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Example

Item Color

T-shirt Red

T-shirt Blue

Polo Red

Polo Yellow

Sweatshirt Blue

Sweatshirt Black

Item Price

T-shirt 12.00

Polo 12.00

Sweatshirt 25.00

Price Tax

12.00 0.60

25.00 1.25

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Tables are now in third normal form


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Relationships

Relationships are created between tablesusing the primary key field and a foreign keyfield

One to One Relationship - One record in atable relates to one record in another table

One to Many Relationship - One record in atable can relate to many records in anothertable

Many to Many Relationship - Many records inone table can relate to many records inanother table

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Relationships in the Example

Item Color

T-shirt Red

T-shirt Blue

Polo Red

Polo Yellow

Sweatshirt Blue

Sweatshirt Black

Item Price

T-shirt 12.00

Polo 12.00

Sweatshirt 25.00

Price Tax

12.00 0.60

25.00 1.25

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One-to-one

One-to-many


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Database Integrity

Primary Key

Clustered

Non-Clustered

Foreign key

Rules and Constraints

Check

Defaults

Triggers

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Thank you!!

gama ilp course ware sdlc data base design new

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