Exam 4: Relational Model Characteristics

What are the characteristics of a relational table?

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

Describe the use of nulls in a database.

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

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

A ____ key can be described as a superkey without unnecessary attributes, that is, a minimal superkey.

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

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

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

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

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

Codd's Rule of ____ states: 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).

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

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).

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

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

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

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

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

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.