Basic Symbols
1
Student Entity type using E-R notation
2
Multivalued – Employee
3
Weak (attributive) entity
4
Example relationships of different degrees
10.5
5
Bill of Materials Unary Relationship
(a) Many-to-Many Relationship
(b) Two Instances
6
CA

Consider the Is_married_to unary relationship
1.
2.
7
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.
1
PERSON
8
Is_Married
_to
Date_Married
2.
PERSON
9
Married
Date_Married
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Optional cardinalities
11
Mandatory Cardinalities
12
One optional, one mandatory cardinality
13
1:M Relationship(ERD)
14
M:M Relationship(tbl)
15
M:M Relationship(ERD)
16
IS-A Relationships(tbl)
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IS-A Relationships (ERD)
18
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.
b.
c.
19
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.
a.
Offer_Date, Offer_Price
Offer_Name
Property_No
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PROPERTY
b.
Offer_Date
Property_No
Offer_No
Offer_Price
Offer_Name
PROPERTY
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OFFER
c.
Offer_Date
Offer_No
Property_No
PROPERTY
Offer_Price
OFFER
Buyer_No
Name
POTENTIAL_
BUYER
Phone_No
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Address
CA - Draw a ER diagram for the
following
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ERD – customer order
Street_Address
City
Name
CUSTOMER
Customer_No
State
Zip
Places
Order_Date
Order_No
ORDER
Promise_Date
Quantity
Includes
Description
Product_No
PRODUCT
Unit_Price
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