DBI202 05

QN=27 (8030) The binary relationship between classes in UML is called ...

• a. Aggregation

• b. Composition

• c. Association

• d. Relation

QN=28 (8231) Consider the Datalog rule H(x,y) <- S(x, y) AND x > 2 AND y < 6. Relation S(x, y) has 3 tuples (2, 3), (3, 5), and (4, 6). What is about H?

• a. H has a tuple (3, 5)

• b. H has a tuple (2, 3)

• c. H has 2 tuples (2, 3) and (3, 5)

• d. H has 3 tuples (2, 3) and (3, 5) and (4, 6)

QN=30 (8232) Suppose that tuple t appears, respectively, x, y, and z times in the relations X, Y, and Z. Let t appear w times in the relation:
X union (Y intersect Z).
Which of the following inequalities is true ?

• a. w <= x+y

• b. w <= y+z

• c. w >= z

• d. w <= max(x,y)

QN=33 (8522) The table Arc(x,y) currently has the following tuples (note there are duplicates):
(See picture)


Compute the result of the query:

SELECT x, COUNT(y)
FROM Arc
GROUP BY x;

Which of the following tuples is in the result?

[file:8522.jpg]

• 
  a. (4,4)

• b. (4,5)

• c. (4,6)

• d. (4,7)

• e. (4,8)

QN=34 (8501) Suppose the relation S(B,C,D) has tuples:

B C D
------------------------------------
a 4 6
c 6 8
c 5 5
e 9 9
F 10 10
c 7 9

Which one of the followings will appear in the result of the following query:

SELECT B, SUM(C)
FROM S
GROUP BY B

• a. (c,11)

• b. (c,13)

• c. (c,12)

• d. (c,18)

QN=35 (8503) Given the relation Employee(SSN, FNAME, LNAME, SALARY, DepartmentNo). Select the right query below to count the number of employees in each department.

• a. SELECT COUNT(*) FROM Employee

• b. SELECT DepartmentNo, COUNT(*) FROM Employee GROUP BY DepartmentNo

• c. SELECT DepartmentNo, COUNT(*) FROM Employee

• d. None of the others

QN=36 (8505) Suppose the relation S(B,C,D) has tuples:

B C D
------------------------------------
a 4 6
c 6 8
c 5 5
e 9 9
f 10 10
c 7 9

What row that appears in the result of the following query:

SELECT SUM(C), SUM(D)
FROM S
WHERE D < 9 AND D > 5

• a. (10,11)

• b. (10,12)

• c. (10,13)

• d. (10,14)

QN=38 (8532) Here are two relations, R(A,B), S(C,D). Their current values are:
R
A B
-------------------
1 4
2 5
8 6
4 7
S
C D
-------------------
0 1
1 0
2 1
5 8
Compute the result of the query:
SELECT A, B, C, D
FROM R RIGHT OUTER JOIN S
ON R.A = S.C
Identify, in the list below, 2 rows that appears in the result.

• a. (null, null, 0, 1)

• b. (null, null, 5, 8)

• c. (8, 6, null, null)

• d. (4, 7, null, null)

QN=39 (8531) Here are three relations, R(A,B), S(C,D). Their current values are:
R
A B
-------------------
1 4
2 5
3 6
4 7

S
C D
-------------------
0 1
1 0
2 1
Compute the result of the query:
SELECT A, B, C, D
FROM R LEFT OUTER JOIN S
ON R.A = S.C
Identify, in the list below, the row that appears in the result.

• a. (4, 7, null, null)

• b. (4, 7, 0, 1)

• c. (4, 7, 1, 0)

• d. (4, 7, 2, 1)

QN=40 (8534) A tuple which fails to participate in a join is called:

• a. dangling tuple

• b. child tuple

• c. parent tuple

• d. neighbor tuple