3.(a) Assume that at the beginning of the semester you made queries to a Univers
ID: 3720640 • Letter: 3
Question
3.(a) Assume that at the beginning of the semester you made queries to a University
database which allowed you to determine that the 25 students initially enrolled in
COMP 596 have an average GPA of 2.96. After Kalvin Smith drops, you performed
the same queries and determined that the remaining 24 students have an average
GPA of 3.00. What can you infer about Smith's GPA? Explain your answer.
(b) This part of the question is based on the statistical database below. Assume no
query size restriction and that a questioner knows that Dodd is a female CS
professor. Show a sequence of two queries that could be used to determine
Dodd’s salary.
(c) Suppose there is a lower query size limit of 2, but no upper limit. Show a
sequence of queries that could be used to determine Dodd’s salary.
(d) The response “sensitive value: response suppressed” is itself a disclosure.
Suggest a way a database management system could suppress responses that
reveal sensitive information without disclosing that the responses to certain
queries are sensitive.
Name
Sex
Department
Position
Salary
Asiema
Male
CS
Professor
80
Clark
Male
Math
Professor
60
Cook
Female
Math
Professor
100
Dodd
Female
CS
Professor
60
Kutukian
Male
EE
Professor
72
Flynn
Female
EE
Professor
88
Manglani
Male
CS
Admin
40
Melkonian
Male
Math
Professor
72
Patel
Female
CS
Student
12
Rees
Male
EE
Admin
80
Smith
Female
Math
Professor
100
Lord
Male
CS
Student
12
Name
Sex
Department
Position
Salary
Asiema
Male
CS
Professor
80
Clark
Male
Math
Professor
60
Cook
Female
Math
Professor
100
Dodd
Female
CS
Professor
60
Kutukian
Male
EE
Professor
72
Flynn
Female
EE
Professor
88
Manglani
Male
CS
Admin
40
Melkonian
Male
Math
Professor
72
Patel
Female
CS
Student
12
Rees
Male
EE
Admin
80
Smith
Female
Math
Professor
100
Lord
Male
CS
Student
12
Explanation / Answer
Ans:
D)
It’s best to return nothing in this case. It is better to return nothing for the query rather than that message because then that is giving something away. For example, if someone is querying a medical history record of someone (and they are unauthorized to see that information), instead of displaying that the response is suppressed, which indicates that they might have something wrong in the record, instead the query could produce nothing, which gives nothing away.
A)
Before Smith's drop the average GPA is 2.96, After droping GPA is 3.0. By Calculating those two scenarios, The GPA of smith is lesser than average GPA, smith's GPA is 2.0
2.96*25=74
3*24=72; 74-72=2;
B)
Assume Table name is PrefessorSalary
-->select salary from PrefessorSalary where name="Dodd";
-->select salary from PrefessorSalary where Department="CS" and name like'D%';
C)
-->select salary from PrefessorSalary where name="Dodd";
-->select salary from PrefessorSalary where Department="CS" and name like'D%';
-->select salary from PrefessorSalary where name IN (select name from Prefessorwhere Department="CS" and name like'D%')
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