CO1 Data Bases

Question 1

What is a data base?

Answer 1

Is a collection of related data stored in a logical and structured manner

Question 2

What is a file(table)?

Answer 2

A collection of related records which contain the same type of info as all other records
Eg info about all students in a class

Question 3

What is a record?

Answer 3

All data relating to one item or thing
Eg info about one student in a class

Question 4

What is a field?

Answer 4

Stores one item of data in a record
Eg a single characteristic about a student (DOB , surname)

Question 5

What are the two types of data bases?

Answer 5

Flat file or relational

Question 6

What are the key points about flat file databases?

Answer 6

Only one table,
No links between them

Question 7

What are the advantages of a flat file data base?

Answer 7

Easy to set up or understand

Question 8

What are the disadvantages of a flat file data base?

Answer 8

Repeated data
Harder to update
No unique attributes
Security is poor

Question 9

What is a relational database?

Answer 9

Has more than one table which are linked together by primary and foreign keys

Question 10

What is a primary key?

Answer 10

Unique identifier

Question 11

what is A foreign key?

Answer 11

Is a primary key in one table which is used as an attribute in another table
/ repeating attribute

Question 12

What is a compound key?

Answer 12

A combination of fields that makes a record unique

Question 13

What is a secondary key?

Answer 13

Made on a field that you would like to be indexed for faster searching
May not be unique are used for sorting or searching

Question 14

What are the advantages of a relational database ?

Answer 14

Data is stored once
Integrity is maintained
Easy to modify
Future proof

Question 15

What are the disadvantages of a relational database?

Answer 15

Difficult to set up

Question 16

What is normalisation (databases)?

Answer 16

Data is split over multiple tables which are related

Question 17

What are the three types of integrity(databases)?

Answer 17

Entity integrity
Referential integrity
Domain integrity

Question 18

What is entity integrity?

Answer 18

Every table must have a primary key which must be unique and not empty

Question 19

What is referential integrity?

Answer 19

foreign keys must point to the primary of another table but cannot be empty meaning there is no relationship

Question 20

What is domain integrity?

Answer 20

all attributes in the database are related to the overall domain that the database is working on

Question 21

What is data redundancy?

Answer 21

refers to the unnecessary duplication of data

Question 22

what is data consistency?

Answer 22

When data is help in more that one file it should be stored in a consistent way

Question 23

What is data independence?

Answer 23

This means that users can view data with out having to be aware of the basic structure of the database

Question 24

What does ERD stand for?

Answer 24

Entity relationship diagram

Question 25

What are entities?

Answer 25

they are tables in a database which are made up of multiple attributes

Question 26

What are Attributes?

Answer 26

Describes the facts, details and characteristics of a entity

Question 27

What are relationships?

Answer 27

Links between entities

Question 28

What are the three types of relationships?

Answer 28

1 to 1
1 to many
many to many

Question 29

What is a one to one relationship?

Answer 29

relationships that are one to another and nothing else

Question 30

What is a one to many relationship?

Answer 30

an example of a one to many is a mother and her children

Question 31

What is a many to many relationship?
(give an example)

Answer 31

an example of a many to many relationship is a book can be loaned by multiple customers and a customer can loan many books

Question 32

how can you get rid of many to many relationships?

Answer 32

they can be removed by adding another entity which acts as a link table
-creates one to many relationships
-makes a relationship into 3NF
-reduces data inconsistencies