Relational Algebra

Question 1

Relational Algebra strikes a good balance between expressive ______ and _______

Answer 1

power and efficiency

Question 2

The 3 standard set-theoretic binary operations are _____, ______, and _______ ________

Answer 2

union, difference, Cartesian product

Question 3

2 unary operations on relations include ______ and _______

Answer 3

projection, selection

Question 4

One special operation on relations is ______

Answer 4

renaming

Question 5

A ________ π_(A1,…,An)(R) chooses columns

Answer 5

projection

Question 6

A ________ σ_θ(R) chooses rows satisfying condition θ

Answer 6

selection

Question 7

A domain of values must be totally _______ to use comparison operators

Answer 7

ordered

Question 8

We use $4 when we do not have attribute names. What does this mean?

Answer 8

Select attribute 4 from a relation

Question 9

It is more efficient to combine multiple _______

Answer 9

selections

Question 10

It is more efficient to nest ______ within ______

Answer 10

selections, projections

Question 11

The cardinality of R x S is…

Answer 11

card(R) * card(S)

Question 12

The arity of R x S is…

Answer 12

arity(R) + arity(S)

Question 13

A _________ ρA->A’ changes the name a an attribute

Answer 13

renaming

Question 14

A _________ _____ |>

Answer 14

natural join

Question 15

A _____ combines all tuples in set together into one table

Answer 15

union

Question 16

An intersection return a table with tuple found in _____ relations

Answer 16

both

Question 17

A _______ A-B removes tuples find in B from A

Answer 17

difference

Question 18

R (intersect) S can be represented as …

Answer 18

R-(R-S)

Question 19

R |>

Answer 19

σ_θ(R×S)

Question 20

Equijoin is the same as ______ join but with a _______ of equalities

Answer 20

theta, conjunction

Question 21

R |>< θ S ==

Answer 21

π_X(R |>

Question 22

R -|>

Answer 22

R − (R |>

Question 23

The 6 primitive operations are…

Answer 23

projection, selection, Cartesian product, renaming, union, and difference

Question 24

A database query language is ___________ ________ if it is at least as expressive as relational algebra

Answer 24

relationally complete

Question 25

SELECT is the same as _____-

Answer 25

projection

Question 26

_______ is the same as cartesian product

Answer 26

FROM

Question 27

WHERE is the same as _______

Answer 27

selection