Chapter 6 Databases HW

Desire to reduce replication

All of the following are reasons for leaving a schema in a lower normal form except

lossless decomposition

For a relational decomposition, the property of being able to get back exactly the original relation by joins is

for each X value there is only one Y value

If X and Y are sets of attributes of relation R, we say that Y is functionally dependent on X if

transitive

If a relation is 2NF but not 3NF, it must have which type of functional dependency?

X is not a superkey

If a relation is 3NF but not BCNF, it must have a non-trivial functional dependency X → A such that

has more rows than the original table

If a relational decomposition is not lossless, doing joins to recreate the original table may produce a table that

{A,B,D} must also be a candidate key for R {A,B} or {A,C} or {B,C} must also be a candidate key for R {A,B,C,D} must also be a candidate key for R Answer: none of these

If set S{A,B,C} is a candidate key for the relation R(A,B,C,D,E), then which of the following must be true

{A,B,C,D} is also a superkey for R

If set S{A,B,C} is a superkey for the relation R(A,B,C,D,E), then

B → C

In a relation R(A, B, C, D), which of the following would prove that R is not 3NF?

every attribute of the universal relation appears in at least one relation

In relational decomposition of a universal relation, the property of attribute preservation requires that

all the attributes on both sides of each dependency appear in the same relation

In relational decomposition of a universal relation, the property of dependency preservation requires that

A → C

In the relation R(A, B, C, D), having the composite key {A,B}, which of the following FDs would demonstrate that the relation is not 2NF?

C → D

In the relation R(A, B, C, D), having the composite key {A,B}, which of the following FDs would demonstrate that the relation is not 3NF?

Decompose R into R1(A,B,C,D) and R2(D)

In the relation R(A,B,C,D) if D is multivalued and the apparent key is A, which of the following is NOT an acceptable way to create a first normal form table for this schema?

the join produces the same tuples as the original relation

In the relational model, a projection is lossless if

is created by a lossy join

In the relational model, a spurious tuple is one that

simple

In the relational model, all of the following are types of dependencies that have been shown to lead to update anomalies EXCEPT

a candidate key a superkey a composite key Answer: none of these

In the relational model, every determinant is always

if two rows have the same A value, they must have the same B value

In the relational model, if A functional determines B, it means that

is lossless, but may not preserve dependencies

It is always possible to find a Boyce-Codd Normal Form decomposition that

3NF

It is always possible to find a dependency preserving lossless decomposition for _______.

3rd

The essence of _______ normal form is that each non-key attribute is functionally dependent on the entire key, and on no other attribute.

3NF

The highest normal form that always allows us to preserve functional dependencies is

synthesis

The normalization process in which we find and group together functional dependencies with the same determinant is called

analysis

The normalization process that starts with a universal relation and uses decomposition to produce a set of normalized relations is called

identifying and removing each violation of BCNF from a universal relation

The standard decomposition algorithm for BCNF requires

The standard mapping of an E-R diagram to a relational model results in a schema that is close to normalized

Using an E-R diagram can be helpful in designing a normalized schema because

a superkey of one of the relations

We can ensure that a binary decomposition is lossless if the set of common attributes in the two relations is

improving efficiency

Which of the following is not one of the major objectives of normalization?

Normalization

_______ means putting a relation into a higher normal form.

composite key

A _______ key is a key that consists of more than one attribute.

candidate

A _______ key is a superkey such that no proper subset of its attributes is itself a superkey.

trivial

A functional dependency in which the attributes on the right hand side are included in the determinant is called

no nonkey attribute is dependent on another nonkey attribute

A relation having only one candidate key is third normal form if it is 2NF and

every determinant is a superkey

A relation is Boyce-Codd Normal Form if

every attribute is single-valued for each tuple the domains of the attributes are atomic each cell of the table can contain only one value Answer: all of these

A relation is first normal form if

first

A relation is in _______ normal form if, and only if, every attribute is single-valued for each tuple.

every nonkey attribute is dependent on the entire key

A relation is second normal form if it is 1NF and