Ch 1 Practice exam

One characteristic of generalization hierarchies is that they are implemented as ______ relationships.

1:1

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

Cartesian

Dr. Codd's ____ rule of relational database states that every value in a table is guaranteed to be accessible through a combination of table name, primary key value, and column name.

Guaranteed access

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

JOIN

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

M:N

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

Natural

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

SELECT

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

True

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

attribute

An index key can have multiple _____ (a composite index).

attributes

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 _____ key selected to uniquely identify all other attribute values in any given row.

candidate

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

closure

Each table _____ represents an attribute.

column

Proper _____ design requires carefully defined and controlled data redundancies to function properly.

data warehousing

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

A(n) ____ links tables on the basis of an equality condition that compares specified columns of each table.

equijoin

Each column has a specific range of values known as the row domain.

false

The SELECT operator yields a vertical subset of a table.

false

The idea of determination is unique to the database environment.

false

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.

false

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

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 _____ is crucial to controlling data redundancy.

foreign keys

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

homonym

A(n) _____ is an orderly arrangement used to logically access rows in a table.

index

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

inner join

Referential _____ dictates that the foreign key must contain values that match the primary key in the related table, or must contain null.

integrity

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

key and row

In a relational model, ____ are also used to establish relationships among tables and to ensure the integrity of the data.

keys

According to Codd's _____ rule of relational database, "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)."

logical data independence

According to Codd's _____ rule of relational database, "If the system supports low level access to the data, users must not be allowed to bypass the integrity rules of the database."

nonsubversion

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

not null

_____ are especially useful when you are trying to determine what values in related tables cause referential integrity problems.

outer joins

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

predicate

_____ returns only the attributes requested, in the order in which they are requested.

project

Rows are sometimes referred to as _____.

records

The word _____, also known as a dataset in Microsoft Access, is based on the mathematical set theory from which Codd derived his model.

relation

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

select

A _____ is a key that can uniquely identify any row in the table.

superkey

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

synonyms

Character data type also known as string data type, can contain any character or symbol not intended for mathematical manipulation, but character sets can include digits or a numeric string.

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

Primary keys are required in relational databases to ensure entity integrity.

true

RDBMSs enforce integrity rules automatically.

true

The DIFFERENCE operator subtracts one table from the other.

true

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.

true

The database designer has two main options when defining a composite table's primary key: use the combination of foreign keys or create a new primary key.

true

When two or more tables share the same number of columns, and when their corresponding columns share the same or compatible domains, they are said to be _____ .

union-compatible

A _____ index is an index in which the index key can have only one pointer value (row) associated with it.

unique

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

unique