DA CH 3

If one department chair—a professor—can chair only one department, and one department can have only one department chair. The entities PROFESSOR and DEPARTMENT exhibit a(n) _____ relationship.

1:1

one characteristic of generalization hierarchies is that they are implemented as ____ relationships

1:1

the ___ relationship should be rare in any relational database design

1:1

the ___ relationship is the "relational model ideal"

1:M

the ____ relationship is the relationship database norm

1:M

The 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.

entity

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

system catalog

the SELECT operator yields a vertical subset of a table

false

the idea of determination is unique to the database environment

false

the order of rows and columns is important to the DBMS

false

the row's range of permissible values is known as its domain

false

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

flags

a ___ is the primary key of one table that has been placed into another table to create a common attribute

foreign key

the proper use of ___ keys is crucial to controlling data redundancy

foriegn

in a database context, the word ___ indicates the use of the same attribute name to label different attributes

homonym

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

Julian

___ relationships cannot be implemented as such in a relational model

M:N

____ relationships can be implemented by creating a new entity in 1:M relationships with the original entities

M:N

in a relational table, each column has a specific range of values known as the ___ domain

attribute

another name for a composite entity is a(n) ___ entity

bridge

a ___ key can be described as a minimal superkey, a superkey without any unnecessary attributes

candidate

a primary key is a(n) ___ key chosen to be the primary means by which rows of a table are uniquely identified

candidate

each table ___ represents an attribute

column

a ___ contains at least all of the attribute names and characteristics for each table in the system

data dictionary

a(n) provides a detailed description of all tables found within the user/ designer- created database

data dictionary

character data can contain any character or symbol intended for mathematical manipulations

false

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

false

only a single attribute, not multiple attributes, can define functional dependence

false

the 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 the primary key

false

referential ___ dictates that the foriegn key must contain values that match the primary key in the related table, or must contain null

integrity

in a relational model, ___ are used to establish relationships among tables and to ensure the integrity of the data

keys

in the relational model ___ are important because they are used to ensure that each row in a table is uniquely identifiable

keys

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

not null

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

predicate

a table is also called ___ because the relational model's creator E.F. Codd, used the two terms as synonyms

relation

a ___ key is defined as a key that is used strictly for data retrieval purposes

secondary

a ___ is any key that uniquely identifies each row

superkey

The _____ catalog can be described as a detailed system data dictionary that describes all objects within the database, including data about table names, the table's creator and creation date, the number of columns in each table, the data type corresponding to each column, index filenames, index creators, authorized users, and access privileges.

system

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

true

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).

true

RDBMs enforce integrity rules automatically

true

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

true

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

true

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

true

each table in a relational database must have a primary key

true

relational algebra defines the theoretical way of manipulating table contents using relational operators

true

the DIFFERENCE operator subtracts one table from the other

true

the DIVIDE operation uses one single column table as the divisor and one two column table as the dividend

true

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

true

you can think of a table as a persistent representation of a logical relation

true

proper data ___ design requires carefully defined and controlled data redundancies to function properly

warehousing