Database Quiz#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 idea of determination is unique to the database environment. (T/F)

False

The order of the rows and columns is important to the DBMS. (T/F)

False

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

M:N

_____ relationships cannot be implemented as such in the relational model.

M:N

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

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

PROJECT

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

Predicate

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

SELECT

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

SELECT

As rare as 1:1 relationships should be, certain conditions absolutely require their use. (T/F)

True

Each table in a relational database must have a primary key. (T/F)

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). (T/F)

True

RDBMSs enforce integrity rules automatically. (T/F)

True

Relational algebra defines the theoretical way of manipulating table contents using relational operators. (T/F)

True

The DIFFERENCE operator subtracts one table from the other. (T/F)

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 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. (T/F)

True

You can think of a table as a persistent representation of a logical relation. (T/F)

True

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

candidate

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

closure

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

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

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

flags

The proper use of _____ keys is crucial to controlling data redundancy.

foreign

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

foreign key

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

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

homonym

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 row in a table is uniquely identifiable.

keys

According to Codd's _____ rule of relational databases, 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

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

natural

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

nonsubversion

A table is also called a(n) _____ 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

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

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

system catalog

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(n) _____ 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

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

warehousing