WEEK 10Database Design

Agenda – Week 10ReviewHybrid ReviewTable Instance ChartsPrimary KeysNormalization

Database Design Steps Review

Determine the purpose of the database

Determine the entitiesDetermine the fields & keysDetermine the relationshipsRefine the design

This is an iterative process that is completed several times

ReviewEntities are….Attributes are….Primary key is…..Foreign key is ……

Information is accessed according to its structure, not its location

Use keys to identify relationships

Planning the DesignERD –

◦Serves as a blueprint for implementation

◦Reduces problems resulting from poor design

◦Determines how data is stored◦Ensures that the design meets the

user’s needs

ReviewSolution to Hybrid Homework

TABLE INSTANCE CHARTS

Table Instance Chart Sample One chart completed for each

table

◦Wk10_TableInstanceChart.xlsx

ExerciseCreate table instance chart for:

◦the puzzle (together)

TYPES OF DATA

Common Data Types in AccessAutonumberTextMemoNumberCurrencyDate/TimeYes/No

AutonumberUse for unique sequential

numberingCommonly used for PKIncrements by 1Automatically inserted when a

record is added.

TextUsed for text or combinations of

text and numbers, such as addresses, or for numbers that do not require calculations, such as phone numbers, part numbers, or postal codes.

Stores up to 255 characters.

MemoUse for lengthy text and

numbers, such as notes or descriptions.

Should be used sparingly

Stores up to 65,536 characters (if not more)

NumberUse for data to be included in

mathematical calculations, except calculations involving money (use Currency type).

Yes/NoUse for data that can be only one

of two possible values, such as ◦Yes/No, ◦True/False, ◦On/Off.

Null values are not allowed

ExerciseCreate table instance chart for:

◦Wine Database

◦Curling Bonspiel scenario

RELATIONSHIPS

Three Basic Types of RelationshipsOne to One (1:1)

One to Many (1:M)

Many to Many (M:M)

Called the cardinality of the relationship◦The cardinality indicates the maximum

number of relationships between the entities, therefore "many" can be explained as "one or many" or sometimes "zero, one, or many".

One to One Relationships1:1 relationships exists when a

single record in one table has 1 and only 1 corresponding record in another table, and vice versa

One to One ExampleA voter can cast only one vote in

an election. A ballot paper can belong to only

one voter. So there will be a 1:1 relationship

between a Voter and a Ballot Paper.

Voter Ballot

One to Many RelationshipsMost common

1:m or m:1

Relationship exists when a record can relate to 1 or more records in a second table but.. A record in the 2nd table can only relate to 1 record in the first table

One to Many ExampleA person can own more than one

car. A car can only have one owner.

Owner Vehicle

Many to Many RelationshipsM:M

Relationship exists when a record in either table can relate to more than one record in the other table

Many to Many ExampleA student can have more than

one professor; the same professor can have many students

Student Professor

Resolving Many to ManyM:M is not allowedWe create a junction or joiner

entityThe name of the joiner entity is

often a combination of the 2 entities

Student ProfessorStud_Prof

Many to Many Relationships

Relationship Review

Normalization Refining the ERD

Task of analyzing entities and the relationships created have been formalized into a process called normalization.

Exercise: ERD & Relationships

Draw an ERD for the puzzle◦Describe the relationships using the

following formatSource Entity

Destination Table

Relationship Type

Describe the relationship in your own words

Customer Movie Rental

Movie Rental

customer

Movie Movie Rental

Movie Rental

Movie

Exercise: ERD & Relationships

Draw an ERD for the wine scenario◦Describe the relationships using the

following format

◦Describe the relationships in the curling bonspiel

Source Entity

Destination Table

Relationship Type

Describe the relationship in your own words

Review Relationship EssentialsNeed a primary key

Need a foreign key ◦A foreign key is a column in a table used to

reference a primary key in another table.

Not all tables will require a foreign key

Primary key and foreign keys are essential when you create relationships that join together multiple tables in a database

Build TimeFor each of the following

scenarios:◦Create and write out a business

narrative ◦Create list of tables◦Create the attributes for the table◦Create a simple ERD and the

relationship rules◦Create a table instance chart

ScenariosPolitical CanvassingHuman Resource Dept.Private Elementary SchoolYoga Studio

*** note each database should be around 5 tables

Access DBCreate a databaseCreate tablesBuild relationshipsPopulate tables

Hybrid / HomeworkHybrid: Refer to the 14 Week

schedule

Database Assignment Part 1

Quiz Time