ISM3212 CH3

Another name for a composite entity is a ____ entity.

Bridge

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

FALSE

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.

FALSE

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

FALSE

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

FALSE

The SELECT operator yields a vertical subset of a table.

FALSE

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

FALSE

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

FALSE

____ yields only the rows that appear in both tables.

INTERSECT

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

Julian

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

Logical

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

Logically, physically

The ____ relational type is the "relational model ideal.

One to Many

____ yields a vertical subset of a table.

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

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 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.

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

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

TRUE

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

TRUE

DBMSs use indexes for many different purposes.

TRUE

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

TRUE

RDBMSs enforce integrity rules automatically.

TRUE

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

TRUE

The DIFFERENCE operator subtracts one table from the other

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.

TRUE

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

UNION

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

data dictionary

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

equal

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

functionally dependent on

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

inner

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

integrity

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

key attribute

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

keys

"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"

nonsubversion

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

null

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

null

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.

primary

Controlled ____ makes a relational database work.

redundancy

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

system catalog

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

table

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

unique