Question 1

Question 1

Give examples of systems in which it may make sense to use traditional file processing instead of a database approach [3]

Answer 1

1. Small internal utility to locate files
2. Small single user application that does not require security (e.g. customised calculator or personal address & phone book)
3. Real-time navigation system (with heavy computation & very little data)

Question 2

Discuss integrity constraints violated by the operation:

Insert into EMPLOYEE

Answer 2

No constraint violations

Question 3

Discuss integrity constraints violated by the operation:

Insert < ‘ProductA’, 4, ‘Bellaire’, 2 > into PROJECT

Answer 3

Violates referential integrity because DNUM=2 and there is no tuple in the DEPARTMENT relation with DNUMBER=2. We may enforce the constraint by:

(i) rejecting the insertion of the new PROJECT tuple,
(ii) changing the value of DNUM in the new PROJECT tuple to an existing DNUMBER value in the DEPARTMENT relation, or
(iii) inserting a new DEPARTMENT tuple with DNUMBER=2.

Question 4

Discuss integrity constraints violated by the operation:

Insert < ‘Production’, 4, ‘943775543’, ‘01-OCT-88’ > into DEPARTMENT

Answer 4

Violates both the key constraint and referential integrity. Violates the key constraint because there already exists a DEPARTMENT tuple with DNUMBER=4. We may enforce this constraint by:
(i) rejecting the insertion, or
(ii) changing the value of DNUMBER in the new DEPARTMENT tuple to a value that does not violate the key constraint.
Violates referential integrity because MGRSSN=’943775543’ and there is no tuple in the EMPLOYEE relation with SSN=’943775543’. We may enforce the constraint by:
(i) rejecting the insertion,
(ii) changing the value of MGRSSN to an existing SSN value in EMPLOYEE, or
(iii) inserting a new EMPLOYEE tuple with SSN=’943775543’

Question 5

Discuss integrity constraints violated by the operation:

Insert < ‘677678989’, null, ‘40.0’ > into WORKS_ON

Answer 5

Violates both the entity integrity and referential integrity. Violates entity integrity because PNO, which is part of the primary key of WORKS_ON, is null. We may enforce this constraint by:
(i) rejecting the insertion, or
(ii) changing the value of PNO in the new WORKS_ON tuple to a value of PNUMBER that exists in the PROJECT relation.
Violates referential integrity because ESSN=’677678989’ and there is no tuple in the EMPLOYEE relation with SSN=’677678989’. We may enforce the constraint by:
(i) rejecting the insertion,
(ii) changing the value of ESSN to an existing SSN value in EMPLOYEE, or
(iii) inserting a new EMPLOYEE tuple with SSN=’677678989’.

Question 6

Discuss integrity constraints violated by the operation:

Insert < ‘453453453’, ‘John’, M, ‘12-DEC-60’, ‘SPOUSE’ > into DEPENDENT

Answer 6

No constraint violations

Question 7

Discuss integrity constraints violated by the operation:

Delete the WORKS_ON tuples with ESSN= ‘333445555’

Answer 7

No constraint violations

Question 8

Discuss integrity constraints violated by the operation:

Delete the EMPLOYEE tuple with SSN= ‘987654321’

Answer 8

Violates referential integrity because several tuples exist in the WORKS_ON, DEPENDENT, DEPARTMENT, and EMPLOYEE relations that reference the tuple being deleted from EMPLOYEE. We may enforce the constraint by:

(i) rejecting the deletion, or
(ii) deleting all tuples in the WORKS_ON, DEPENDENT, DEPARTMENT, and EMPLOYEE relations whose values for ESSN, ESSN, MGRSSN, and SUPERSSN, respectively, is equal to’987654321’

Question 9

Discuss integrity constraints violated by the operation:

Delete the PROJECT tuple with PNAME= ‘ProductX’

Answer 9

Violates referential integrity because two tuples exist in the WORKS_ON relations that reference the tuple being deleted from PROJECT. We may enforce the constraint by:

(i) rejecting the deletion, or
(ii) deleting the tuples in the WORKS_ON relation whose value for PNO=1 (the value for the primary key PNUMBER for the tuple being deleted from PROJECT)

Question 10

Discuss integrity constraints violated by the operation:

Modify the MGRSSN and MGRSTARTDATE of the DEPARTMENT tuple with DNUMBER=5 to ‘123456789’ and ‘01-OCT-88’, respectively.

Answer 10

No constraint violations

Question 11

Discuss integrity constraints violated by the operation:

Modify the SUPERSSN attribute of the EMPLOYEE tuple with SSN= ‘999887777’ to ‘943775543’

Answer 11

Violates referential integrity because the new value of SUPERSSN=’943775543’ and there is no tuple in the EMPLOYEE relation with SSN=’943775543’. We may enforce the constraint by:

(i) rejecting the deletion, or
(ii) inserting a new EMPLOYEE tuple with SSN=’943775543’

Question 12

Discuss integrity constraints violated by the operation:
Modify the HOURS attribute of the WORKS_ON tuple with ESSN= ‘999887777’ and
PNO= 10 to ‘5.0’

Answer 12

No constraint violations