topic: databases

Question 1

define a foreign key and its use

Answer 1

• its a primary key from one table used as an attribute in another table
• it links tables / represent relationship

Question 2

define a primary key

Answer 2

• a unique identifier

Question 3

describe the form a table has to be in for it to be in 1NF

Answer 3

each field has a unique name
no fields representing grouped data
data is atomic
has a primary key/ each record is unique

Question 4

describe the form a table has to be in for it to be in 2NF

Answer 4

Is in First Normal Form
Every field is dependent on every part of the primary key - if primary key is not composite this will be met already

Question 5

describe the form a table has to be in for it to be in 3NF

Answer 5

data is in the 2NF
non-key field depend only on the one primary key

Question 6

what’s one advantage and one disadvantage in indexing a random field

Answer 6

pro - Searches of the field can be performed more quickly
con - The index takes up extra space
in the database

Question 7

The user’s password is passed to a function that generates a hash and the result is stored in
passwordHash.
Describe what is meant by the term ‘hash’.

Answer 7

a result generated by applying an algorithm/numeric
process to a value

Question 8

what is a pro of storing a password as a hash

Answer 8

hash functions are one way/can’t be reverse
if someone gains access to the database they cannot
access user’s password