ER Modeling Practice Exercise Solutions

MBA 8473

PROBLEM 1. (This is just one way of doing this problem. Other versions are possible depending on what assumptions you make).

ASSUMPTIONS:

(It will be beneficial to think about what a ‘car’ means in this situation. Is it a car? Or, is it a sold-car? Etc.)1. VIN# provides unique identification2. Year of make can be found from VIN#3. PRE-OWNED is a yes/no attribute

1. MODEL-TYPE is unique2. We are going to capture only the latest

recall info3. Etc. etc.

ENTITIES:

CARVIN#ARRIVAL-

DATEDEALER-PRICEPRE-OWNEDSELL-TIME-

STAMP...MODEL

MODEL-TYPESTART-DATELAST RECALL...

1. We do not want to use ss# as unique identifier2. To be a customer in the database the person

should have bought at least one car.Etc etc.

CUSTOMERCUSTOMER-ID-NUMBERCUST1-F-NAMECUST1-L-NAME…

PROBLEM 1 continued:

ER Model

bought

MODEL

Has aRelationship related assumptions:1. One customer can buy many cars over time2. A car can be bought by one customer only3. To be a customer one has to buy a car4. A car can have only one model5. Etc. Etc.

CUSTOMER SOLD-CAR0Is bought by

Can belong to

PROBLEM 2.Note that the ERD solution for problem 1 can meet most of the requirements of problem 2 except the fact that we do not need model info for problem 2.Only kink in this problem was the use of USED-CARS and NEW-CARS. In this particular case it is convenient to capture that as an attribute called PRE-OWNED (yes/no) like I already did for problem 1.Another way to treat this in the ERD will be to recognize two sub-type entities viz., USED-CARAnd NEW-CAR for a super entity called CAR. Can be done like this:

CAR

USED-CAR NEW-CAR

Is a

PROBLEM 3. (This is just one way of doing this problem. Other versions are possible depending onwhat assumptions you make). Partial solution only.

ENTITIES:

CUSTOMER

SOFTWARE

SOFTWARE-TYPE

BETA-STAGE (all beta-stage types may not be used at a given point of time)

SALES-AGENT

PROMOTION

(PROMOTION-TYPE+DATE is unique identifier)

Hints for the relationships:

Customer and Software – zero/many to zero/many

Software-type and Beta-stage – one to one (assumption: a given software type can only be in a one beta)

Customer and Sales-agent – (many to one) See P&G example from class notes.

Promotions (are sent to ) Customers – Many to many.

You should be able to fill the rest from this!

SOFTWARE and SOFTWARETYPE – one/one to one/one

PROBLEM 3 continued:

ER Model

Can buyCUSTOMER SOFTWARE0 SOFTWARE-TYPE

PROMOTIONSSALES-AGENT BETA-STAGE

0Was a

Receives Can be in a

0

0

Is assigned to