INFORMATION SYSTEM HOMEWORK . THE HOMEOWRK ABOUT The Bank of Elk River,

   

3.5.2 Entity Relationship Diagrams

            3.5.2.1 Entity

            3.5.2.2 Key based

            3.5.2.3 Fully attributed

            3.5.2.4 Fully described (cannot fit on one page, rather one page per entity)

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Basic Symbols

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Student Entity type using E-R notation

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Multivalued – Employee

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Weak (attributive) entity

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Example relationships of different degrees
10.5

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Bill of Materials Unary Relationship
(a) Many-to-Many Relationship
(b) Two Instances

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CA
Consider the Is_married_to unary relationship
Assume we want to know the date on which a marriage occurred. Augment this ER diagram to include a Date_married attribute.
Since sometimes persons remarry after the death of a spouse or divorce, redraw this ERD to show the whole history of marriages for person. Show the Date_married attribute on this diagram.

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2.

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Optional cardinalities

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Mandatory Cardinalities

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One optional, one mandatory cardinality

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1:M Relationship(ERD)

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M:M Relationship(tbl)

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M:M Relationship(ERD)

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IS-A Relationships(tbl)

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IS-A Relationships (ERD)

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CA
In a real state DB, there is an entity called PROPERTY, which is a property for sale by the agency. Each time a potential property buyer makes a purchase offer on a property, the agency records the date, offering price, and name of the person making the offer.
Represent the PROPERTY entity and its purchase offer attributes using the notation for multivalued attributes.
Represent the PROPERTY entity and its purchase offer attributes using two entity types.
Finally, assume the agency decides to also keep data about buyers and potential buyers, including their name, phone number, and address. Augment your answer to part b above to accommodate this new entity type.

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a.

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b.

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c.

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CA – Draw a ER diagram for the following

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ERD – customer order

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PERSON

Is_Married
_to

Date_Married

PERSON

Married

Date_Married

PROPERTY

Offer_Date, Offer_Price

Offer_Name

Property_No

OFFER

Property_No

PROPERTY

Offer_No

Offer_Date

Offer_Price

Offer_Name

OFFER

Property_No

PROPERTY

Offer_No

Offer_Date

Offer_Price

OFFER

Property_No

PROPERTY

Offer_No

Offer_Date

Offer_Price

POTENTIAL_

BUYER

Buyer_No

Phone_No

Address

Name

PRODUCT

CUSTOMER

ORDER

Places

Includes

Name

Customer_No

Street_Address

City

State

Zip

Order_No

Order_Date

Promise_Date

Quantity

Product_No

Description

Unit_
Price