Lecture 8: Relational Data Model

Question 1

Formal term for table , column, and row is

Answer 1

relation, attribute, tuple

Question 2

All possible column values are called

Answer 2

domain

Question 3

table definition is

Answer 3

schema of a relation

Question 4

populated table

Answer 4

state of the relation

Question 5

a relation must have a key and we can not find one

Answer 5

we create one sequentially

Question 6

key of a relation role is

Answer 6

uniquely identifies that row in the table

Question 7

columns represents the attribute which gives…

Answer 7

meaning to the data

Question 8

row is a representation if

Answer 8

certain facts that correspond to a real world entity or relationship

Question 9

Schema of a relation is denoted by

Answer 9

R(A1,A2…,An)

Question 10

Schema is database is denoted by

Answer 10

S={R1,R2,…,Rn}

-R is the relation schema

Question 11

Tuples are not considered to be

Answer 11

ordered even though they appear to be in a tabular form

Question 12

all values in a tuple are …

Answer 12

considered atomic

Question 13

each value must be from the domain of the attribute (T or F)

Answer 13

T

Question 14

A null represent

Answer 14

unknown or inapplicable to certain tuples

Question 15

Constraints are conditions that must hold all valid relation states (t or f)

Answer 15

t

Question 16

the three main types of constraints are

Answer 16

• key constraint
• entity integrity constraint
• referential integrity constraint

Question 17

implicit constraint

Answer 17

is the domain constraint

Question 18

superkey is a set

Answer 18

set of attributes SK of R with the following condition

Question 19

(t or f) two tuples in any valid relation state can have the same value for superkey

Answer 19

f

Question 20

a super key can be one or more (t or f)

Answer 20

t

Question 21

a key is a

Answer 21

minimal superkey

Question 22

any key is a superkey (t or f)

Answer 22

t

Question 23

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

Answer 23

t

Question 24

a minimal superkey is a key ( t or f)

Answer 24

t

Question 25

primary key can be null values ( t or f)

Answer 25

f , it cant be null values

Question 26

can foreign key attribute be null value ?

Answer 26

Yes , any other attribute that are not primary key has to right to do not null constraint nor just primary key attributes

Question 27

if a relation is referencing another using foreign keys then it can't use values other than one in the relation its referencing (t or f)

Answer 27

t

Question 28

in referencing relation there's an attribute called foreign key that reference the primary key of the referenced relation ( t or f)

Answer 28

t

Question 29

Values of the FK can be one of the two things .... , ....

Answer 29

null, values exists in the referenced relation

Question 30

A FK should not be a part of its primary key (t or f)

Answer 30

true, it's a different primary key but the fk is just there for connection zy ma bnrsm fel schema arrow lel FK bas bn3ml underline 3la another primary key

Question 31

Semantic integrity is

Answer 31

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

Question 32

a constraint specification language allows ...

Answer 32

triggers

Question 33

in case of integrity violations several actions can be taken

Answer 33

- 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 34

Insert may violate in

Answer 34

domain constraint, key constraint, entity integrity

Question 35

Delete may violate in

Answer 35

if a primary key is being deleted is referenced from other tuples in the database

Question 36

Update may violate in

Answer 36

domain constraint and not null constraint an attribute being modified

Question 37

a tuple is an ordered set of values

Answer 37

enclosed in angled brackets