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Exam 3: The Relational Database Model

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Question 31

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A data dictionary is sometimes described as "the database designer's database" because it records the design decisions about tables and their structures.

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Question 32

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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.

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Question 33

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

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

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.

In a relational table, each column has a specific range of values known as the _____ domain.

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

PRODUCT yields all possible pairs of rows from two tables, also known as the _____ product.

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

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

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

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.

A(n) _____ index is an index in which the index key can have only one pointer value (row) associated with it.

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

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.

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

RDBMSs enforce integrity rules automatically.

Describe the use of null values in a database.

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

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