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mMpn Exercises

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mMpn Exercises

Database Principles

PAYMENT

SeqNum

LOAN

LoanID

CUSTOMER

CustID

(0,n)

(1,1)

(1,1)

(1,n)

- A car loan to a customer is paid back by regular monthly, numbered payments. Payments are identified by which loan and which payment number.

Database Principles

PERSON

SSN

PLAYER

position

COACH

is_a

is_a

trains

(1,1)

(1,n)

- Baseball teams consist of players and coaches. The former are known to play different positions. All players have a coach responsible for their training.

Database Principles

ACCOUNT

BRANCH

AcctNum

Name

CUSTOMER

SSN

held with

(0,n)

(1,1)

(c,d)

(a,b)

(1,n)

- Must a customer have accounts with only 1 branch?
- Do branches share responsibility for accounts?

(e,f)

opens

(g,h)

(1,n)

No. h == n and c == 1

No. d == 1

Database Principles

(e,f)

(0,n)

qualified to repair

PLANETYPE

TypeName

(1,n)

(g,h)

(a,b)

(1,1)

is of type

MECHANIC

SSN

(c,d)

repaired by

PLANE

PlaneID

(0,n)

(1,n)

(k,l)

date

(0,n)

(I,j)

- What is the obvious mistake in the above diagram?
- Does the model support the enterprise rule that there should always be a mechanic able to repair any plane in need?

(c,d)=(0,n). It should be (1,1)

No, e=0, a=1 implies there may be a planeand no mechanic qualified to repair it.

Database Principles