CITS1402
10. Suppose that a relation
R
(
A, B, C, D, E
) satisfies the following functional depen-
dencies
D
→
C,
CE
→
A,
D
→
A,
AE
→
D.
Which of the following is a
key
for the relation
R
?
(a)
AD
(b)
BE
(c)
BD
(d)
BDE
(e)
CDE
lOMoARcPSD|2860748

11. Suppose that a database scheme has two tables
R
(
A, B
) and
S
(
B, C
) where all
values are integers. Consider the three relational expressions
I
π
A,C
(
R ⊲⊳ σ
B
=1
(
S
))
II
π
A,C
(
π
A
(
R
)
×
σ
B
=1
(
S
))
III
π
A
(
σ
B
=1
(
R
))
×
π
C
(
σ
B
=1
(
S
))
Which of the following statements about the three expressions is true for all
instances of
R
and
S
?

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Semester 2 Supplementary/Deferred Examinations
February 2016
9.
CITS1402
12. The various keywords of a
SELECT
query must occur in a particular order, or else
the query will simply generate a syntax error.
Assuming that a query has no
subqueries, then which of the following is the correct order?
lOMoARcPSD|2860748

13. Suppose that two tables
R
and
S
are created with the following MySQL com-
mands
CREATE TABLE R(c INT PRIMARY KEY, d INT);
CREATE TABLE S(a INT PRIMARY KEY, b INT, FOREIGN KEY (b) REFERENCES R(c));
Suppose that
R
contains the tuples (1
,
1), (2
,
4), (3
,
9) and (4
,
16) while
S
contains
the tuples (0
,
1), (1
,
2) and (2
,
4).
Which of the following statements will complete without error?
1.
UPDATE R SET c = c+1 WHERE d > 10;
2.
INSERT INTO S VALUES (3,7);
3.
INSERT INTO S VALUES (2,3);

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Semester 2 Supplementary/Deferred Examinations
February 2016
10.
CITS1402
14. Consider three transactions running at approximately the same time on a table
R(x)
, where
x
is of type
INT
— the
COMMIT
statements indicate where each
transaction ends.
SELECT SUM(x) FROM R;
COMMIT;
INSERT INTO R VALUES(5);
INSERT INTO R VALUES(10);
INSERT INTO R VALUES(15);
COMMIT;
DELETE FROM R WHERE x=15;
DELETE FROM R WHERE x=10;
COMMIT;
If the table originally contained integers summing to 100, none of which are
5, 10 or 15, then which of the following values
cannot
be returned by the
first
transaction
if all three transactions run with isolation level
SERIALIZABLE
?
(a) 75
(b) 100
(c) 105
(d) 130
(e) All of the values are possible.