Integrity constraints

Question 1

what is Data Model ?

Answer 1

Storage technique to provide data independence.

Question 2

first codd rule?

Answer 2

Data must be stored in tabular format.

Question 3

What is Attribute?

Answer 3

Attributes describe the instances in the row of a database

Question 4

what is a tuple

Answer 4

Is nothing but a record in one coloumn

Question 5

what is Arity ?

Answer 5

Number if fields or attributes i.e no of column in a database table.

Question 6

What is cardinality ?

Answer 6

Cardinality is nothing but number of records present ina database table.

Question 7

domain attribute ?

Answer 7

set of possible values accepted by an attribute.

such as varchar, number, int , date etc.

Question 8

what is emp(eid,ename)

Answer 8

Its known as relational schema.. that describes structure of a table.

Question 9

what is relational instance ?

Answer 9

Record set of database (snapshot) at any instance of time. that is what is present inside the table.

Question 10

rule2?of codd

Answer 10

No two records of rdbms table must be same

Question 11

Candidate key?

Answer 11

Minimal set of attributes that represent every tuple of a database table uniquely. Its come due to codd second rule.

Question 12

alternative keys ?

Answer 12

Attributes other than primary key are known as Ak

Question 13

unknwn value are stored as ______ in rdbms table ?

Answer 13

null

Question 14

candidate key whose field values are not allowed to null,

and atmost one such key is allowed in any relational table is known as _____?

Answer 14

Primary key

Question 15

In RDBMS table there must be atleast one Candidate key whose field value is ____?

Answer 15

not null

Question 16

candidate key with only one attribute __ ?

candidate key with more than one attribute___ ?

Answer 16

simple candidate key

compound or composite key

Question 17

Prime attribute ?

Answer 17

Attributes whoch belongs to some candidate key of relational schema.

Question 18

Super key is practical concept?T/F

Answer 18

F

Question 19

Set of attributes of relational schema which differentiate records uniquely are known as ____ ?

Answer 19

Super key

Question 20

Minimum possible superkey ?

Answer 20

1 … all the attributes of a relational schema is always a superkey

Question 21

Maximum possible super key?

Answer 21

2^n-1.. when each attributes of a relational schema is a candidate key.

Question 22

R(a,b,c,d,e)

how many super key in R if (a,bc ) is candidate key?

Answer 22

20

Question 23

super key which has minimal attributes

Answer 23

candidate key

Question 24

foreign key or referential key?

Answer 24

used to relate data between two tables

Question 25

set of attributes references to primary key of another relation is____?

Answer 25

foreign key

Question 26

foreign key is defined over two relation referential relation and referenced relation FK is in which relation ?

Answer 26

referential relation

Question 27

Foreign key allows null values ? T/F

Answer 27

T

Question 28

what is the mapping between referenced relation and referential relation ?

Answer 28

1:M

Question 29

Referential Intigrity constraints referenced relation 1. insertion ____? 2.deletion a.______? b_____? c______?

Answer 29

1. no violation | 2. on delete no action b. on delete cascade c.ondelete set null

Question 30

Referential integrity constraint also known as ____?

Answer 30

foreign key

Question 31

what is subset dependencies ?

Answer 31

referential integrity constraint

Question 32

Some integrity constraints of SQL ?

Answer 32

not null unique check primary key

Question 33

______ is a predicate that we expect the database to always satisfy.

Answer 33

Assertion

Question 34

syntax of assertion

Answer 34

create assertion assertion_name check "predicate"

Question 35

______ used to improve quality of data entered into database

Answer 35

data integrity constraint

Question 36

To add integrity constraint we use___

Answer 36

alter

Question 37

syntax for alter

Answer 37

alter table name add constraints

Question 38

domain constraint, Functional dependencies and referential integrity constraint are special form of ____ ?

Answer 38

Assertion.