Deck 3: The Relational Database Model

Question 1

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 1

True

Question 2

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

Answer 2

True

Question 3

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 3

True

Question 4

All RDBMSs enforce integrity rules automatically.

Question 5

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

Question 6

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

Question 7

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

Question 8

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

Question 9

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

Question 10

A proper understanding of the concept and use of keys in a relational database model is very important.

Question 11

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 12

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

Question 13

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

Question 14

The SELECT operator yields a vertical subset of a table.

Question 15

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 16

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

Question 17

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

Question 18

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

Question 19

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

Question 20

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

Question 21

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

Question 22

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

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

Question 23

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

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

Question 24

DBMSs use indexes for many different purposes.

Question 25

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 26

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 27

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

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

Question 28

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 29

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 30

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

Question 31

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

Question 32

A data dictionary contains metadata-data about data.

Question 33

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

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

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.

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

Question 35

The DIFFERENCE operator subtracts one table from the other.

Question 36

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

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

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 39

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

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

Question 40

The DIVIDE operation uses one single-column table (i.e.column "a")as the divisor and one two-column table (i.e.columns "a" and "b")as the dividend.

Question 41

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 42

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

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

Question 43

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

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

Question 44

Controlled ____ makes a relational database work.

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

Question 45

In the following table description,____ is the primary key.
PRODUCT (PROD_CODE,PROD_DESCRIPT,PROD_PRICE,PROD_ON_HAND,VEND_CODE)

A) PROD_DESCRIPT
B) PROD_CODE
C) PROD_PRICE
D) PROD_ON_HAND

Question 46

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 47

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 48

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 49

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

A) foreign
B) unique
C) composite
D) complete

Question 50

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 51

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 52

____ yields only the rows that appear in both tables.

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

Question 53

A ____ is a textual representation of the database tables where each table is listed by its name followed by the list of its attributes in parentheses.

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

Question 54

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 55

A ____ is any key that uniquely identifies each row.

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

Question 56

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

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

Question 57

____ yields a vertical subset of a table.

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

Question 58

____,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 59

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 60

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

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

Question 61

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 62

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 63

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 64

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

Question 65

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 66

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

Question 67

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

Question 68

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 69

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 70

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 71

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

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

Question 72

____ relational type is the "relational model ideal."

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

Question 73

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 74

Attribute A determines attribute B (that is,B is functionally ____________________ on A)if all of the rows in the table that agree in value for attribute A also agree in value for attribute B.

Question 75

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 76

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

Question 77

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

Question 78

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

Question 79

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 80

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

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