Deck 3: The Relational Database Model

Question 1

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

Answer 1

False

Question 2

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

Answer 2

False

Question 3

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

Answer 3

False

Question 4

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.

Question 5

The SELECT operator yields a vertical subset of a table.

Question 6

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.

Question 7

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

Question 8

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

Question 9

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

Question 10

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

Question 11

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

Question 12

The idea of determination is unique to the database environment.

Question 13

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

Question 14

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

Question 15

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

Question 16

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).

Question 17

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

Question 18

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.

Question 19

RDBMSs enforce integrity rules automatically.

Question 20

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

Question 21

The DIFFERENCE operator subtracts one table from the other.

Question 22

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.

Question 23

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

A) table
B) rowset
C) attribute
D) intersection

Question 24

The relational model's creator,E.F.Codd,used the term relation as a synonym for ____.

A) index
B) key
C) table
D) relationship

Question 25

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.

A) contains
B) is related to
C) owns
D) determines

Question 26

In the relational model,____ are important because they are used to ensure that each row in a table is uniquely identifiable.

A) relations
B) keys
C) indexes
D) logical structures

Question 27

Current relational database software generally provides only a system catalog (and not a data dictionary).

Question 28

A data dictionary contains metadata-data about data.

Question 29

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

A) Epoch
B) Calendar
C) Julian
D) logical

Question 30

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

Question 31

DBMSs use indexes for many different purposes.

Question 32

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.

Question 33

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

A) Logical
B) Character
C) Date
D) Numeric

Question 34

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

A) key attribute
B) logical attribute
C) key determiner
D) selector

Question 35

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

Question 36

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

Question 37

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.

Question 38

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

A) logically dependent on
B) owned by
C) determined by
D) functionally dependent on

Question 39

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

A) relationally, hierarchically
B) hierarchically, relationally
C) physically, logically
D) logically, physically

Question 40

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

A) Predicate
B) Database
C) Relational
D) Index

Question 41

In an outer join,the matched pairs would be retained and any unmatched values in the other table would be left ____.

A) in another table
B) null
C) out of the results
D) with matching values from the original table

Question 42

____ yields a vertical subset of a table.

A) PROJECT
B) SELECT
C) UNION
D) DIFFERENCE

Question 43

The ____ constraint can be placed on a column to ensure that every row in the table has a value for that column.

A) HAS VALUE
B) NOT NULL
C) MUST HAVE VALUE
D) NOT EMPTY

Question 44

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

A) meta dictionary
B) schema
C) data dictionary
D) system catalog

Question 45

Controlled ____ makes a relational database work.

A) relations
B) logic
C) chaos
D) redundancy

Question 46

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

A) INTERSECT
B) UNION
C) DIFFERENCE
D) SELECT

Question 47

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

A) integrity
B) uniqueness
C) direction
D) relations

Question 48

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.

A) entity
B) referential
C) complete
D) null

Question 49

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

A) secondary
B) candidate
C) primary
D) foreign

Question 50

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

A) *
B) <
C) =
D) >

Question 51

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

A) zero
B) a foreign key
C) null
D) a candidate key

Question 52

____ combines all rows from two tables,excluding duplicate rows.

A) INTERSECT
B) UNION
C) DIFFERENCE
D) SELECT

Question 53

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

A) outer
B) inner
C) direct
D) union

Question 54

A ____ key is defined as a key that is used strictly for data retrieval purposes.

A) lookup
B) foreign
C) candidate
D) secondary

Question 55

____ yields only the rows that appear in both tables.

A) INTERSECT
B) UNION
C) DIFFERENCE
D) SELECT

Question 56

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

A) equal
B) unique
C) foreign
D) natural

Question 57

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

A) INTERSECT
B) UNION
C) DIFFERENCE
D) SELECT

Question 58

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

A) data dictionary
B) relational schema
C) logical schema
D) join

Question 59

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

A) nil
B) null
C) empty
D) zero

Question 60

A ____ is any key that uniquely identifies each row.

A) superkey
B) special
C) selective
D) candidate

Question 61

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

A) 1:1
B) 1:M
C) M:1
D) M:N

Question 62

____________________ is the real power behind the relational database,allowing the use of independent tables linked by common attributes.

Question 63

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

A) entity
B) duplicate
C) synonym
D) homonym

Question 64

The ____ relational type is the "relational model ideal."

A) 1:1
B) 1:M
C) M:1
D) M:N

Question 65

In the relational model,____________________ are important because they are used to ensure that each row in a table is uniquely identifiable.

Question 66

In a database context,the word ____ indicates the use of the same attribute name to label different attributes.

A) redundancy
B) homonym
C) duplicate
D) synonym

Question 67

The following example exhibits ____________________ integrity:
The CUSTOMER table's primary key is CUS_CODE.The CUSTOMER primary key column has no null entries,and all entries are unique.Similarly,the AGENT table's primary key is AGENT_CODE,and this primary key column also is free of null entries.

Question 68

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

A) key
B) incomplete
C) unique
D) primary

Question 69

A(n)____________________ key can be described as a superkey without unnecessary attributes.

Question 70

To avoid nulls,some designers use special codes,known as ____________________,to indicate the absence of some value.

Question 71

PRODUCT yields all possible pairs of rows from two tables-also known as the ____________________ product.

Question 72

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

A) table
B) superkey
C) relationship
D) index

Question 73

If the foreign key contains either matching values or nulls,the table that makes use of that foreign key is said to exhibit ____________________ integrity

Question 74

The relational operators have the property of ____________________;that is,the use of relational algebra operators on existing relations (tables)produces new relations.

Question 75

Codd's Rule of ____ states: Application programs and ad hoc facilities are logically unaffected when changes are made to the table structures that preserve the original table values (changing order of columns or inserting columns).

A) Nonsubversion
B) Logical Data Independence
C) Comprehensive Data Sublanguage
D) Integrity Independence

Question 76

The logical view of the relational database is facilitated by the creation of data relationships based on a logical construct known as a(n)____________________.

Question 77

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

A) Nonsubversion
B) Logical Data Independence
C) Comprehensive Data Sublanguage
D) Integrity Independence

Question 78

Since it is used to link the tables that originally were related in a M:N relationship,the composite entity structure includes-as foreign keys-at least the ____ keys of the tables that are to be linked.

A) composite
B) super
C) primary
D) unique

Question 79

In a relational table,each column has a specific range of values known as the ____________________ domain.

Question 80

Another name for a composite entity is a ____ entity.

A) bridge
B) linked
C) directive
D) referring