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Basic Symbols. Student Entity type using E-R notation. Multivalued – Employee . Weak (attributive) entity. Example relationships of different degrees. 10. 5. Bill of Materials Unary Relationship. (a) Many-to-Many Relationship. (b) Two Instances. CA. - PowerPoint PPT Presentation
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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
1. Assume we want to know the date on which a marriage occurred. Augment this ER diagram to include a Date_married attribute.
2. 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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1
PERSON
Is_Married_to
Date_Married
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2.
PERSON
Married Date_Married
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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.a. Represent the PROPERTY entity and its purchase offer attributes
using the notation for multivalued attributes.b. Represent the PROPERTY entity and its purchase offer attributes
using two entity types.c. 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.
PROPERTY
Offer_Date, Offer_Price Offer_Name
Property_No
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b.
OFFER
Property_No
PROPERTY
Offer_No
Offer_Date
Offer_Price
Offer_Name
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c.
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
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CA - Draw a ER diagram for the following
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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
ERD – customer order
