Exam 3: The Relational Database Model

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

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

Describe the use of null values in a database.

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

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

Define entity integrity. What are the two requirements to ensure entity integrity?

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

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

A(n) provides a detailed description of all tables found within the user/designer-created database.

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

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

The relationship should be rare in any relational database design.

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

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.

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.

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

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.

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

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