What does the expression $\_$B$>5(\_$A$,$ B$($R$))$ return?

$21$

a$.$

All tuples from R

b$.$

An empty relation

c$.$

None of these

d$.$

Values of A where B $>5$

e$.$

Rows where B is greater than $5,$ showing only A and B

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$22$

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In the context of $1$NF$,$ which of the following is a valid attribute type?

$22$

a$.$

None of these.

b$.$

Simple attributes

c$.$

Multivalued attributes

d$.$

Composite attributes

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$23$

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What is the primary requirement for a relation to be in First Normal Form $(1$NF$)?$

$23$

a$.$

It must be free of multivalued dependencies.

b$.$

There must be no transitive dependencies.

c$.$

All attributes must contain atomic values and it must be free of multivalued dependencies.

d$.$

All attributes must contain atomic values.

e$.$

None of these

f$.$

It must have a primary key.

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$24$

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Which of the following is NOT a characteristic of a relation in $1$NF$?$

$24$

a$.$

It can contain multivalued attributes.

b$.$

All entries in a column are of the same type.

c$.$

It might have a unique identifier $($primary key$).$

d$.$

None of these

e$.$

Each cell must contain only one value.

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$25$

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What is the effect of a lossless join on query performance?

$25$

a$.$

It always improves performance

b$.$

It can simplify queries but may not always improve performance

c$.$

It has no effect on performance

d$.$

None of these

e$.$

It always complicates queries

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$26$