EPFL - Databases - Quiz 5

Normalization

1) Which of the following notions is not an intergrity constraint
Candidate keys
Foreign keys
Functional dependencies
Indexes

2) If X, Y, Z are the attributes of a relation R, such that X → Y, and Y → Z, then which of the following functional dependencies must also hold on R?
X → YZ
Z → X
YZ → X
Z → Y

3) If X, Y, Z are the attributes of a relation R, such that X → Y, and Z → Y, then which of the following decompositions is lossy?
XY and YZ
XZ and YZ
XZ and XY
none of these

4) If X, Y, Z are the attributes of a relation R, such that X → Y, and Z → Y, then which of the following decompositions preserves dependencies?
XZ and YZ
XY and YZ
XZ and XY
none of these

5) If X, Y, Z are the attributes of a relation R, such that X → Y, and Y → Z, then which of the following decompositions are not in BCNF?
XZ and YZ
XZ and XY
XY and YZ
none of these

Concurrency

6) A schedule is called serializable if it is equivalent to:
another possible schedule
all other schedules
a serial schedule
all serial schedules

7) Strict 2PL locking does not allow:
non-serializable schedules
serial schedules
serializable schedules
all conflict serializable schedules

8) A schedule is conflict serializable if and only if its dependency graph is
fully connected
cyclic
acyclic
bi-partite

9) Which 2 lock types are compatible at the same level of granularity?
exclusive-exclusive
shared-exclusive
shared-shared
exclusive-shared

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