Chapter 3

Question 1

The practical significance of taking the logical view of a database is that it serves as a reminder of the simple file concept of data storage.

Answer 1

True

Question 2

Because the relational model uses attribute values to establish relationships among tables, many database users correctly assume that the term relation refers to such relationships.

Answer 2

False

Question 3

Numeric data are data on which you can perform meaningful arithmetic procedures.

Answer 3

True

Question 4

Each table in a relational database must have a primary key.

Answer 4

True

Question 5

In a relational model, if A determines B, C, and D, you write A = B, C, D.

Answer 5

False

Question 6

If the attribute (B) is functionally dependent on a composite key (A) but not on any subset of that composite key, the attribute (B) is fully functionally dependent on (A).

Answer 6

True

Question 7

There is never a good reason to use null values in a database.

Answer 7

False

Question 8

Tables within a database share common attributes that enable the tables to be linked together.

Answer 8

True

Question 9

RDBMSs enforce integrity rules automatically.

Answer 9

True

Question 10

The SELECT operator yields a vertical subset of a table.

Answer 10

False

Question 11

The DIFFERENCE operator subtracts one table from the other.

Answer 11

True

Question 12

A left outer join on tables CUSTOMER and AGENT yields all of the rows in the CUSTOMER table, including those that do not have a matching value in the AGENT table.

Answer 12

True

Question 13

Which of the following is used to select partial table contents?

Answer 13

SELECT
FROM
BY ;

LIST
FROM
BY ;

-SELECT
FROM
WHERE ;

LIST
FROM
WHERE ;

Question 14

Which query will output the table contents when the value of V_CODE is not equal to 21344?

Answer 14

-SELECT P_DESCRIPT, P_INDATE, P_PRICE, V_CODE
FROM PRODUCT
WHERE V_CODE <> 21344;

SELECT P_DESCRIPT, P_INDATE, P_PRICE, V_CODE
FROM PRODUCT
WHERE V_CODE <= 21344;

SELECT P_DESCRIPT, P_INDATE, P_PRICE, V_CODE
FROM PRODUCT
WHERE V_CODE = 21344;

SELECT P_DESCRIPT, P_INDATE, P_PRICE, V_CODE
FROM PRODUCT
WHERE V_CODE => 21344;

Question 15

Which query will output the table contents when the value of the character field P_CODE is alphabetically less than 1558-QW1?

Answer 15

-SELECT P_CODE, P_DESCRIPT, P_QOH, P_MIN, P_PRICE
FROM PRODUCT
WHERE P_CODE

Question 16

You can think of a table as a persistent representation of a logical relation.

Answer 16

True

Question 17

The order of the rows and columns is important to the DBMS.

Answer 17

False

Question 18

Character data can contain any character or symbol intended for mathematical manipulation.

Answer 18

False

Question 19

The idea of determination is unique to the database environment.

Answer 19

False

Question 20

Only a single attribute, not multiple attributes, can define functional dependence.

Answer 20

False

Question 21

A null is created when you press the Enter key or the Tab key to move to the next entry without making a prior entry of any kind.

Answer 21

True

Question 22

Depending on the sophistication of the application development software, nulls can create problems when functions such as COUNT, AVERAGE, and SUM are used.

Answer 22

True

Question 23

A foreign key must exist in both tables that have a relationship.

Answer 23

False

Question 24

Referential and entity integrity are two names for the same thing.

Answer 24

False

Question 25

Tables must have the same attribute characteristics (the columns and domains must be compatible) to be used in a UNION.

Answer 25

True

Question 26

The DIFFERENCE operator subtracts one table from the other.

Answer 26

True

Question 27

In a natural join, the column on which the join was made occurs twice in the new table.

Answer 27

False

Question 28

The DIVIDE operation uses one single-column table (e.g., column “a”) as the divisor and one two-column table (e.g., columns “a” and “b”) as the dividend.

Answer 28

True

Question 29

A data dictionary contains metadata—data about data.

Answer 29

True

Question 30

A data dictionary is sometimes described as “the database designer’s database” because it records the design decisions about tables and their structures.

Answer 30

True

Question 31

The one-to-many (1:M) relationship is easily implemented in the relational model by putting the foreign key of the “1” side in the table of the “many” side as a primary key.

Answer 31

False

Question 32

As rare as 1:1 relationships should be, certain conditions absolutely require their use.

Answer 32

True

Question 33

DBMSs use indexes for many different purposes.

Answer 33

True

Question 34

____ logic, used extensively in mathematics, provides a framework in which an assertion (statement of fact) can be verified as either true or false.

Answer 34

Predicate

Question 35

The relational database model enables you to view data ____ rather than ____.

Answer 35

Logically, physically

Question 36

A(n) ____ is perceived as a two-dimensional structure composed of rows and columns.

Answer 36

Table

Question 37

Date attributes contain calendar dates stored in a special format known as the ____ date format.

Answer 37

Julian

Question 38

____ data can have only a true or false (yes or no) values.

Answer 38

Logical

Question 39

In the context of a database table, the statement “A ____ B” indicates that if you know the value of attribute A, you can look up the value of attribute B.

Answer 39

determines

Question 40

The attribute B is ____ the attribute A if each value in column A determines one and only one value in column B.

Answer 40

functionally dependent on

Question 41

Any attribute that is part of a key is known as a ____.

Answer 41

key attribute

Question 42

No data entry at all is known as a(n) ____.

Answer 42

null

Question 43

Controlled ____ makes a relational database work.

Answer 43

redundancy

Question 44

Referential ____ means that if the foreign key contains a value, that value refers to an existing valid tuple (row) in another relation.

Answer 44

integrity

Question 45

A ____ key can be described as a superkey without unnecessary attributes, that is, a minimal superkey.

Answer 45

candidate

Question 46

All primary key entries are unique, and no part of a primary key may be ____.

Answer 46

null

Question 47

A CUSTOMER table’s primary key is CUS_CODE. The CUSTOMER primary key column has no null entries, and all entries are unique. This is an example of ____ integrity.

Answer 47

entity

Question 48

To be considered minimally relational, the DBMS must support the key relational operators ____, PROJECT, and JOIN.

Answer 48

SELECT

Question 49

____, also known as RESTRICT, yields values for all rows found in a table that satisfy a given condition.

Answer 49

SELECT

Question 50

____ yields a vertical subset of a table.

Answer 50

PROJECT

Question 51

____ yields only the rows that appear in both tables.

Answer 51

INTERSECT

Question 52

A(n) ____ join links tables by selecting only the rows with common values in their common attribute(s).

Answer 52

natural

Question 53

The equijoin takes its name from the comparison operator ____ used in the condition.

Answer 53

=

Question 54

A(n) ____ join only returns matched records from the tables that are being joined.

Answer 54

inner

Question 55

A ____ contains at least all of the attribute names and characteristics for each table in the system.

Answer 55

data dictionary

Question 56

The ____ is actually a system-created database whose tables store the user/designer-created database characteristics and contents.

Answer 56

system catalog

Question 57

In a database context, a(n) ____ indicates the use of different names to describe the same attribute.

Answer 57

synonym

Question 58

The ____ relational type is the “relational model ideal.”

Answer 58

1:M

Question 59

The ____ relationship should be rare in any relational database design.

Answer 59

1:1

Question 60

Another name for a composite entity is a ____ entity.

Answer 60

bridge

Question 61

A(n) ____ is an ordered arrangement of keys and pointers.

Answer 61

index

Question 62

When you define a table’s primary key, the DBMS automatically creates a(n) ____ index on the primary key column(s) you declared.

Answer 62

unique

Question 63

Codd’s Rule of ____ states: If the system supports low-level access to the data, users must not be allowed to bypass the integrity rules of the database

Answer 63

Nonsubversion