Database

Database

Logical Database Design has 30 Questions
The entity integrity rule states that:

no primary key attribute may be null.
no primary key can be composite.
no primary key may be unique.
no primary key may be equal to a value in a foreign key.
An enterprise key is a primary key whose value is unique for a given relation.

True
False
When mapping a many-to-many unary relationship into a relation which of the following is true?

One relation is created.
Two relations are created.
Three relations are created.
Four relations are created.
A composite attribute does not get mapped into a relation.

True
False
If no multivalued attributes exist and no partial dependencies exist in a relation, then the relation is in what normal form?

First normal form
Second normal form
Third normal form
Fourth normal form
A relation is a two-dimensional table.

True
False
A foreign key is which of the following?

Any attribute
The same thing as a primary key
An attribute that serves as the primary key of another relation
An attribute that serves no purpose
Weak entities do not get mapped into a relation.

True
False
A transitive dependency is which of the following?

A functional dependency between two or more key attributes.
A functional dependency between two or more nonkey attributes.
A relation that is in first normal form.
A relation that is in second normal form.
A primary key may be null.

True
False
A null value is assigned when no other value applies.

True
False
When mapping a multivalued attribute into a relation which of the following is true?

One relation is created.
Two relations are created.
Three relations are created.
Four relations are created.
A synonym is two or more attributes that have different names but the same meaning.

True
False
If no multivalued attributes exist in a relation, then the relation is in what normal form?

First normal form
Second normal form
Third normal form
Fourth normal form
The primary key in a relation does not need to be underlined.

True
False
A primary key is which of the following?

Any attribute
An attribute that uniquely identifies each row
An attribute that uniquely identifies each column
A derived attribute
In a 1:M relationship, the primary key on the one side migrates to the many side to become the foreign key on the many side.

True
False
The relational model consists of:

data in the form of tables.
data redundancy.
operations using non-SQL languages.
unorganized data.
Normalization is a formal process for deciding which attributes should be grouped together in a relation.

True
False
When mapping a binary many-to-many relationship into a relation which of the following is true?

One relation is created.
Two relations are created.
Three relations are created.
Four relations are created.
A candidate key must uniquely identify each row.

True
False
A relation has which of the following properties?

Each row is not unique.
Attributes can have the same name within a given table.
Each relation has a unique name.
The order of the columns is significant.
Well-structured relations encourage anomalies of data.

True
False
When mapping a ternary relationship with an associative entity into a relation which of the following is true?

One relation is created.
Two relations are created.
Three relations are created.
Four relations are created.
A foreign key may be null and still adhere to the referential integrity constraint.

True
False
When mapping a regular entity into a relation which of the following is true?

One relation is created.
Two relations are created.
Three relations are created.
Four relations are created.
If a relation is in third normal form, it does not need to be in second normal form.

True
False
When mapping a supertype/subtype relationship which of the following is true?

The supertype primary key is assigned to each subtype.
The subtype primary key is assigned to each supertype.
There is no link between the supertype/subtype entities.
There is no primary key/foreign key relationship between a supertype/subtype.
The primary key of the new relation in a many-to-many relationship is a composite key comprised of the primary keys of each of the binary entities.

True
False
Relations are:

two-dimensional tables.
three-dimensional tables.
four-dimensional tables.
five-dimensional tables.