1.3.2 Databases

Question 1

relational database

Answer 1

based on linked tables to avoid data duplication, inconsistency, redundancy and improving data integrity and security

Question 2

Flat file database

Answer 2

database that consists of a single file

Question 3

cons of flat file databases

Answer 3

it can be very inefficient due to data redundancy, it is difficult to query and takes up unnecessary space

Question 4

primary key

Answer 4

a unique identifier for each record in the table, each row of the primary key must be different

Question 5

foreign key

Answer 5

it is the attribute that links two tables together, it exists in one table as the primary key and acts as a foreign key in another

Question 6

secondary key

Answer 6

allows a database to be searched quickly, but typically does not uniquely identify a record with complete accuracy. For if you want to find a student in a database you would probably search for their name so the secondary key/index would be the NAME field

Question 7

ACID

Answer 7

Atomicity, Consistency, Isolation and Durability

Question 8

Atomicity

Answer 8

A transaction should either be completely transformed or not at all. A half completed change must not be saved back to the database

Question 9

Consistency

Answer 9

each transaction must obey the defined validation rules of the database, to maintain referential integrity

Question 10

isolation

Answer 10

A transaction must not be interrupted by another transaction. The transaction must occur in isolation so other user or processes cannot access the data concerned

Question 11

Durability

Answer 11

once a transaction has begun, it must be completed under all circumstances

Question 12

referential integrity

Answer 12

the idea of keeping a database consistent by ensuring that changes made to data with a table are accounted for in all linked tables

Question 13

Normalisation

Answer 13

The formal process of optimally designing data tables by reducing redundancy and repetition by converting them into normal forms

Question 14

First normal form (1NF)

Answer 14

1. All fields must be unique/different
2. values in fields must be the same domain/data type
3. Values in fields should be atomic ( contains one value )
4. No two records should be identical
5. each table needs a primary key

Question 15

composite key

Answer 15

Two or more primary keys used in a table that can uniquely identify each record

Question 16

Second normal form (2NF)

Answer 16

1. The data is already in 1NF

2. Any partial dependencies(one or more fields depend on only part of the primary key ) have been removed

Question 17

Third normal form (3NF)

Answer 17

1. The data is in 2NF

2. Remove any non-key dependency

Question 18

Record locking

Answer 18

A technique used to prevent simultaneous access to data in a database