Db Design Clc

8/3/2019 Db Design Clc

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Dr Tran Thi Song Minh National Economics University

4.3 CREATING A DATABASEENVIRONMENT


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KEY TERMS

A Database = a collection of information that youorganize and access according to the logical structure ofthat information.

A relational database = a database that uses a seriesof logically related two-dimensional tables or files to store

information in the form of a database. A relation = often used to refer to a file while designing

a DB

A Entity class = A concept typically people, places, orthings about which you wish to store information and thatyou can identify with an unique key (called a primary key)

A primary key= A field (or group of fields in somecases) that uniquely describes each record/ an instance.

An instance = An occurrence of an entity class that canbe uniquely described with a primary key.


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KEY TERMS (Contd)

A intersection relation/ a composite relation = arelation you create to eliminate a many-to-manyrelationship.

A composite primary key= a primary key thatconsists of the primary fields from the twointersecting relations.

A foreign key= a primary key of one file (relation)that appears in another file (relation).


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FOUR STEPS IN DESIGNING ANDBUILDING A RELATIONAL DATABASE

1. Defining entity classes and primarykeys

2. Defining relationships and cardinalityamong entity classes

3. Defining information (fields) for eachrelation

4. Using a data definition language tocreate your database.


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ENTITY-RELATIONSHIP DIAGRAMSYMBOLS

Entity class

Single relationship

Multiple relationship

A relationship

Zero or optional relationship


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A SUPPLY CHAIN MANAGEMENT REPORTFOR SOLOMON ENTERPRISES

SOLOMON ENTERPRISES

Supply Report Ending October 14, 2005

CONCRETE RAW MATERIAL SUPPLIER

Type Name ID Name Unit QOH ID Name1 Home B Cement paste 1 400 412 Wesley Enterprises

C Sand 2 1200 444 Juniper Sand & Gravel

A Water 1.5 9999 999 N/A

Total 4.5

2 Comm B Cement paste 1 400 412 Wesley Enterprises

C Sand 2 1200 444 Juniper Sand & Gravel

A Water 1 9999 999 N/A

Total 4


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BUSINESS RULES

1. A given concrete type will have many rawmaterials in it.

2. A given raw material may appear in many

types of concrete.3. Each raw material has one and only one

supplier.

4. A supplier may provide many raw

materials. Solomon may have a supplier inits database that doesnt currently provideany raw materials.


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STEP 1: Defining entity classes andprimary keys

Entity classes Primary Key

Concrete Type Concrete Type (ID)

Raw Material Raw Material ID

Supplier Suppler ID

Goal

To define the various entity classes and the primary keysthat uniquely define each record or instance within each entityclass.


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STEP 2: Defining relationshipsamong entity classes

CONCRETE TYPE RAW MATERIAL

SUPPLIER

provides a

is composed of

An Intersection Relation should becreated to remove this many-to-

many relationship

Goal

To define the relationships among the entity classes.


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READING THE Entity-RelationshipDIAGRAM

A Concrete Type is composed of more than one RawMaterial (denoted with the ) and must be composedof at least one Raw Material.

A Raw Material can be used to create more than one

Concrete Type (denoted with the ) but is notrequired to be used to create any Concrete Type.

A Raw Material must be provided by one Supplier(denoted with the first |) denoted with the first |) andcan only be provided by one Supplier (denoted with thesecond |).

A Supplier may not provide any Raw Material (denotedwith the 0) but may provide more than one Material .


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How to create an IntersectionRelation

1. Create a new E-R diagram (showing no cardinality) with theoriginal two relations on each end and a new one (theintersection relation) in the middle.

2. Underneath the intersection relation, write down some of thecomposite primary keys (these will be composed of theprimary keys from the other two relations)

3. Create a meaningfull name (e.g., Bill of Material) for theintersection relation.

4. Move the minimum cardinality appearing next to the leftrelation just to the right of the intersection relation.

5. Move the minimum cardinality appearing next to the rightrelation just to the left of the intersection relation.

6. The maximum cardinality on both side of the intersectionrelation will always be many7. As a general rule, the new minimum and maximum

cardinalities for the two original relations will be the one andone.


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THE COMPLETED E-R-D FOR THESUPLY CHAIN MANAGEMENT

CONCRETE TYPE

RAW MATERIAL

SUPPLIER

provides a

is used for

BILL OF MATERIAL

is composed of


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READING THE ERD DIAGRAM

Concrete Type-Bill of Material From left to right: A Concrete Type can have multiple listings of Raw

Material in Bill of Material and must have a listing of Raw Material in Billof Material.

From right to left : A Concrete Type found in Bill of Material must befound and can be found only one time in Concrete Type.

Raw Material-Bill of Material From left to right: A Raw Material can be found in many Bill of Material

listings but may not be found in any Bill of Material listing. From right to left : A Raw Material found in Bill of Material must be

found and can be found only one time in Raw Material.

Supplier-Raw Material From left to right: A Supplier may not provide any Raw Material

(denoted with the 0) but may provide more than one Material.

From right to left: A Raw Material must be provided by one Supplier(denoted with the first |) and can only be provided by one Supplier(denoted with the second |).


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STEP 3:Defining information(fields) for each relation

Goal

To make sure that the information ineach relation indeed in the correct

relation and that the information can notbe derived from other information.

Technique

Three rules of normalization


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A FIRST LOOK AT THE RELATIONS FOR THESUPPLY CHAIN MANAGEMENT SIDE OFSOLOMONS DATABASE

CONCRETE TYPES RELATION (Concrete type, Type name, RawMaterial Total)

RAW MATERIAL RELATION (Raw Material ID, Raw MaterialName, QOH, Supplier ID, Supplier Name)

SUPPLIER RELATION (Supplier ID, Supplier Name)

BILL OF MATERIAL RELATION (Concrete Type, Raw MaterialID, Unit)


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STEP 4: Using a data definition

language to create your database.

Goal

To take the structure you created in steps 1through 3 and use a data definition

language to actually create the relations.Tool

A Database Management System (MS-Access, Visual FoxPro etc.)

To specify the logical organization for a database

To access and use the information within thedatabase.


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EXERCISES FOR ENTITYRELATIONSHIP DIAGRAMMING

Define the cardinality among thefollowing entity classes

Seminar Section

Seminar

Qualified Teacher

Student

has

teaches

Enrolls in


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YOUR TASK

Create the numerical relationships by addingthe symbols of |, O, and crows foot in theappropriate places

Provide a narrative description of eachnumerical relationship:

Relationship Narrative Description

Seminar-Seminar Section

Seminar-Seminar Section

Qualified Teacher-Seminar Section

Seminar Section-Qualified Teacher

Student-Seminar

Seminar-Student


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EXAMPLES OF NORMALIZATION

Normalization An important technique to designdatabases

The process of creating small, stable, yet flexibleand adaptive data structures from complex groupsof data.

An unnormalizedrelation/ table for concretetypes

Concretetype ConcreteName RawMaterialTotal

RawMaterialID

RawMaterialName

QOH Unit SupplierName SupplierID


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Normalization process

First Normal Form (1.NF)

No repeating sections in the table.

Second Normal Form 2.NF Each nonkey column depends on the whole

key/ entire key.

Third Normal Form 3.NF

Each nonkey column depends nothing butthe key.


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Problem: (Raw Material Total, Raw Material ID, Raw Material Name, QOH, Unit, SupplierName, Supplier ID) is repeated in the unnormalized relation/ table.

First Normal Form: To split out all repeating sections.

CONCRETE TYPES (Concrete type Id, concrete name, Raw material total)

Bill of material (Concrete type Id, Raw Material ID, Raw Material Name, QOH, Unit,Supplier Name, Supplier ID)

The old key included in the new table toconnect the tables back together


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Problem: Every time we enter the Raw Material Id, we have to reenter Raw Material Name, QOH,Supplier Id, Supplier Name)

Second Normal Form: To split the table so that all nonkey columns depend on the whole key (notjust part of it)

Bill of material (Concrete type Id, Raw Material ID, Raw Material Name, QOH, Unit,Supplier Name, Supplier ID)

Bill of material (Concrete type Id, Raw Material ID, Unit)

Raw Material (Raw Material ID, Raw Material Name, QOH, Supplier ID, Supplier Name)

The old key included in the new table to

connect the tables back together


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Problem: Supplier_Name andSupplier_Address depend on thenonkey column Supplier_Number

Third Normal Form: To split the table so that every nonkey columndepends nothing but the key

Raw Material (Raw Material ID, Raw Material Name, QOH,Supplier ID, Supplier Name)

Raw Material (Raw Material ID, Raw Material Name, QOH,Supplier ID)

SUPPLIER(Supplier Id, Supplier Name)

The old key included in the new table toconnect the tables back together


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Data Structure Diagram (DSD)

SUPPLIER

Supplier Id(PK)

Supplier Name

RAW MATERIAL

Raw material Id(PK)

Raw material nameQOH

Supplier Id

BILL OF MATERIAL

Raw material Id

Concrete Type Id

Unit

CONCRETE TYPES

Concrete Type Id(PK)

Type name

Total Raw material

Documents

Db Design Clc