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Exam 3: The Relational Database Model

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Question 31

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A is any key that uniquely identifies each row.

A) superkey
B) special key
C) foreign key
D) candidate key

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Question 32

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

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Question 33

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Define an index.Explain the role of indexes in a relational database.

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

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

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

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

An index key can have multiple (a composite index).

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

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

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

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

What is a key and how is it important in a relational model?

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.

Describe the use of the INTERSECT operator.

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

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

One characteristic of generalization hierarchies is that they are implemented as relationships.

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

The relationship should be rare in any relational database design.