bcis2620 chapter 3

data dictionary

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

superkey

A _____ is any key that uniquely identifies each row.

foreign key

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

candidate

A _____ key can be described as a minimal superkey, a superkey without any unnecessary attributes.

secondary

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

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.

index

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

natural

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

inner join

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

logical data independence

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).

nonsubversion

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.

bridge

Another name for a composite entity is a(n) _____ entity.

true

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

false

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

Julian

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

true

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

column

Each table _____ represents an attribute.

true

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

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).

synonym

In a database context, a(n) _____ indicates the use of different names to describe the same attribute.

homonym

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

false

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

keys

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

false

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

true

RDBMSs enforce integrity rules automatically.

integrity

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

true

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

entity

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.

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.

false

The SELECT operator yields a vertical subset of a table.

NOT NULL

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

system catalog

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

1:M

The _____ relationship is the "relational model ideal."

1:1

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

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.

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.

false

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

SELECT

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

union-compatible

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 _____.

unique

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

true

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

Outer joins

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

Predicate

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

M:N

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

PROJECT

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

SELECT

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