Lecture 8: Relational Database Model

Question 1

Table in formal relational model term is

Answer 1

relation

Question 2

Column header in formal relational model term is

Answer 2

attribute

Question 3

All possible column values in formal relational model term is

Answer 3

domain

Question 4

row in formal relational model term is

Answer 4

tuple

Question 5

in formal relational model the term table definition is

Answer 5

schema of a relation

Question 6

in formal relational model the term populated table

Answer 6

state of relation

Question 7

T or F

a relation can have no key

Answer 7

false

Question 8

Key of a relation identifies what ?

Answer 8

identifies a row in the table

Question 9

schema of a relation is denoted as

Answer 9

R(A1,A2,A3…)

Question 10

T or f

each attribute has a domain or a set of valid values

Answer 10

true

Question 11

t or f

domain has only the logical definition

Answer 11

false, it has a logical definition and also has a datatype or a format

Question 12

a tuple is represented by

Answer 12

enclosed in angled brackets

Question 13

schema of a database is denoted by

Answer 13

S(R1,R2,R3…)

Question 14

t or f

tuples are ordered

Answer 14

false

Question 15

t or f

attributes in a relation schema R and of the values with the tuple are ordered

Answer 15

true

Question 16

t or f

tuple values can be a group of values

Answer 16

false, tuple values must be atomic

Question 17

t or f

each value must be from the domain off the attribute for that column

Answer 17

true

Question 18

t or f

null values represents values that are unknown or inapplicable

Answer 18

true

Question 19

name three main constraints types

Answer 19

• Key constraint
• Entity integrity constraint
• Referential integrity constraint

Question 20

Super key is a

Answer 20

is a set of attributes that are taken collectively and can identify all other attribute uniquely

Question 21

t or f

two tuples can have the same value for their super key

Answer 21

false

Question 22

t or f

a super key can be one or more key

Answer 22

true

Question 23

a key is a minimal

Answer 23

superkey

Question 24

t or f

any super key is a key

Answer 24

false

Question 25

t or f any set of attributes that includes a key is a superkey

Answer 25

true

Question 26

entity integrity is

Answer 26

primary key can't be null values in any tuple

Question 27

referential integrity is

Answer 27

if a relation is referencing another using foreign keys then it can't use values other than one in the relation it's referencing

Question 28

t or f a value of a foreign key can be null

Answer 28

true

Question 29

t or f a value of a foreign key can be a value that doesn't exist in the referenced relation

Answer 29

false

Question 30

t or f a foreign key can be a part of its primary key

Answer 30

false

Question 31

semantic integrity is

Answer 31

based on the application and cannot be expressed by the model per se

Question 32

what language is used in sql 99 to allow triggers and assertion

Answer 32

a constraint specification

Question 33

t or f the relational database state is union of all individual relation states

Answer 33

true

Question 34

t or f if a database is changed the state remain the same

Answer 34

false, if a database changed a new state arises

Question 35

actions that can be taken in integrity constraints violations

Answer 35

- Cancel : the operation that causes the violation - Perform : the operation but inform the user of the violation - Trigger additional updates : so the violation is corrected (Cascade or null) - Execute a user-specified error-correction routine

Question 36

t or f insert may violate the domain constraint

Answer 36

true

Question 37

t or f insert doesn't violate the key constraint

Answer 37

false

Question 38

t or f insert doesn't violate the referential integrity constraint

Answer 38

false

Question 39

t or f insert may violates the entity integrity constraint

Answer 39

true

Question 40

t or f it's legal if a primary key is deleted

Answer 40

false, If a primary key is being deleted is referenced from other tuples in the database

Question 41

if delete is trying to remove a PK what actions can be performed

Answer 41

Restrict: reject the deletion Cascade: to attempt to cascade the deletion by deleting tuples that reference the tuple that is being deleted Set Null or Set Default: set the FK of the referencing tuples to NULL or changed to reference another default valid tuple

Question 42

update may violate .... and ....

Answer 42

domain constraint, and not-null constraint

Question 43

t or f it is legal to update a foreign key

Answer 43

false, may violate referential integrity

Question 44

t or f updating ordinary attributes, doesn't violate any constraints

Answer 44

false, it can violate domain constraint