Chapter 14

Question 1

______________ are used to specify formal measures of the “goodness” of relational designs, and are constraints that are derived from the meaning and interrelationships of the data attributes

Answer 1

Functional Dependencies (FDs)

Question 2

______ are used to define normal forms for relations.

Answer 2

keys

Question 3

Write the FD constraint of the following:
Social security number determines employee name.

Answer 3

SSN → ENAME

Question 4

Write the FD constraint of the following:
Employee ssn and project number determines the hours per week that the employee works on the project

Answer 4

{SSN, PNUMBER} → HOURS

Question 5

T/F: The FD constraint must hold on every relation instance r(R).

Answer 5

True.

Question 6

T/F: If K is a key of schema R, then R functionally determines all attributes in K.

Answer 6

F, K funcitonally determines all attributes in K.

Question 7

T/F: Given an instance (population) of a relation, all we can conclude is that an FD MAY exist between certain attributes.

Answer 7

true.
What we can definitely conclude is – that certain FDs do not exist because there are tuples that show a violation of those dependencies.

Question 8

Find the FDs that may exist in the following:

Answer 8

Question 9

Find the FDs that may exist in the following:

Answer 9

Question 10

____________ is the process of decomposing unsatisfactory “bad” relations by breaking up their attributes into smaller relations.

Answer 10

Normalization

Question 11

__________ is a condition using keys and FDs of a relation to certify whether a relation schema is in a particular normal form.

Answer 11

Normal Form

Question 12

_____________ is the process of storing the join of higher normal form relations as a base relation—which is in a lower normal form.

Answer 12

Denormalization

Question 13

________ is a normal form based on keys, join dependencies (JDs)

Answer 13

5NF

Question 14

________ is a normal form based on keys, multi-valued dependencies (MVDS).

Answer 14

4NF

Question 15

_______, ________, and ________ are normal forms based on keys and FDs of a relation schema.

Answer 15

2NF, 3NF, BCNF

Question 16

T/F: The database designers need to normalize to the highest possible normal form.

Answer 16

false, they do not.
usually up to 3NF and BCNF. 4NF rarely used in practice.

Question 17

A _________ of a relation schema R = {A1, A2, …., An} is a set of attributes S subset-of R with the property that no two tuples t1 and t2 in any legal relation state r of R will have t1[S] = t2[S] .

Answer 17

Superkey

Question 18

A ________ is a superkey with the additional property that removal of any attribute from K will cause K not to be a superkey any more.

Answer 18

Key K

Question 19

If a relation schema has more than one key, each is called a _____________.

Answer 19

candidate key

Question 20

T/F: One of the candidate keys is arbitrarily designated to be the primary key, and the others are called secondary keys.

Answer 20

True.

Question 21

T/F: A Prime attribute must be a member of some candidate key.

Answer 21

true

Question 22

A __________ is not a prime attribute—that is, it is not a member of any candidate key.

Answer 22

nonprime attribute

Question 23

The First Normal form disallows ________ attributes, ___________ attributes, and nested relations; attributes whose values for an individual tuple are non-atomic.

Answer 23

composite. multivalued.

Question 24

Normalize the following into 1NF:

Answer 24

Question 25

Normalize the following:

Answer 25

we decomposed the nested relation EMP_PROJC into two relations EMP_PROJ1 and EMP_PROJ2 by propagating the primary key.

Question 26

________ is an attribute that is member of the primary key K.

Answer 26

prime attribute

Question 27

______________ is when an FD Y -> Z where removal of any attribute from Y means the FD does not hold any more.

Answer 27

Full functional dependency

Question 28

Is the following a full FD? or not?
{SSN, PNUMBER} -> ENAME

Answer 28

it is not a full FD (it is called a
partial dependency ) since SSN -> ENAME also holds

Question 29

Is the following a full FD or not?
{SSN, PNUMBER} -> HOURS

Answer 29

it is a full FD since neither SSN -> HOURS nor PNUMBER -> HOURS hold

Question 30

A relation schema R is in second normal form (2NF) if every non-prime attribute A in R is fully functionally dependent on the __________.

Answer 30

primary key