SQL

Question 1

Declarative language

Answer 1

describes the data we are interested in, without describing the control flow to access it

Question 2

Wildcard characters

Answer 2

used with Where clause, % matches zero or more characters, _ matches an single character

Question 3

BETWEEN operator

Answer 3

inclusive and operation, equivalent to >= and <=

Question 4

Joins

Answer 4

an operator for combining tuples from two or more table

Question 5

Cross join

Answer 5

also called inner join, join, provides every possible combination between two tables unless an ON clause is provided

Question 6

Alias

Answer 6

used to identify a table or column by another name, uses AS keyword

Question 7

Natural join

Answer 7

automatically joins on equality between attributes with the same name between tables (implicit join condition)

Question 8

Outer join

Answer 8

allow us to retain tuples that would otherwise be discarded, attributes from tuples that do not match take on NULL values, can be left, right, or full

Question 9

Self join

Answer 9

used to join a table with itself to show a relationship, aliasing is required

Question 10

Three Tier Architecture

Answer 10

database tier connects to an application tier which connects to a presentation tier