Databases

Question 1

Relational Database

Answer 1

A database which recognises the difference between entities by creating different tables for each entity

Question 2

Entity

Answer 2

An item of interest of which information is stored

Question 3

Attributes

Answer 3

Link tables together and are the charcteristics of the entity

Question 4

Flat File

Answer 4

A database structure which has a single file and its attributes.

Question 5

Primary Key

Answer 5

A unique identifier for each record in the table

Question 6

Foreign Key

Answer 6

A attribute which links two tables together

foreign key will exist in one table as the primary key and act as the foreign key in another

Question 7

Secondary Key

Answer 7

Allows databases to be searched quickly

{Order and Search}

(Index)

Question 8

ERM (Entity Relationship Modelling)

Answer 8

Relationships between tables are shown in abstracted view

Question 9

Relationships

Answer 9

defined by how many records they associate with in each table.

One-to-One
One-to-Many
Many-to-Many

Question 10

Normalisation

Answer 10

The process of coming up with the best possible layout for a relational database

Question 11

Normalisation Rules:

Answer 11

1. no redundancy (unnecessary duplicates)
2. Consistent data throughout linked tables.
3. Records can be added and removed without issues.
4. Complex queries (requests) can be carried out.

Question 12

First normal Form

Answer 12

There must be no attribute that has more than 1 value

Question 13

Second normal Form

Answer 13

A database which doesn’t have any partial dependencies and is in First Normal Form.

 This means that no attributes can depend on part of a
composite key (multiple keys in one used to identify rows).

Question 14

Third normal Form

Answer 14

Database is in Second Normal form and contains no non-key dependencies it is in Third Normal Form.

Non-key dependency - the attribute only depends on the value of the primary key and nothing else.

Question 15

Indexing

Answer 15

method used to store the position of each record ordered by a certain attribute.
Used to look up and access data quickly.
The primary key is automatically indexed

(but primary key is almost never queried as its forgotten. so secondary keys are used. Secondary keys are indexed to make the table easier and faster to search through on those particular attributes.)

Question 16

Capturing Data

Answer 16

data needs to be inputted. there’s lots of ways of doing this and the way you choose to input data depends on the context.

surveys - data is manually entered
checks scanned using - Magnetic Ink Character Recognition (MICR).
multiple choice questions - Optical Mark Recognition (OMR)

Question 17

Selecting and Managing Data

Answer 17

selecting correct data is important part of data pre-processing

only selecting data that fits a certain criteria using SQL to sort and manage the data

Question 18

Exchanging Data

Answer 18

is the process of transferring collected data

EDI (Electronic Data Interchange) transfers data without human interaction from node to node

Question 19

Referential Integrity

Answer 19

process of ensuring consistency.

ensures data isnt removed if it is required elsewhere in a linked table

Question 20

Transaction Processing

Answer 20

a single operation executed on data.

Question 21

ACID

Answer 21

Atomicity
Consistency
Isolation
Durability

Question 22

Atomicity

Answer 22

A transaction must be processed in its entirety or not at all

Question 23

Consistency

Answer 23

transaction must maintain the referential integrity rules between linked tables

Question 24

Isolation

Answer 24

Simultaneous execution of transactions must lead to the same result as if they were executed one after the other.

Question 25

Durability

Answer 25

Once a transaction has been executed it will remain so

even if the power if cut off

Question 26

Record Locking

Answer 26

process of preventing simultaneous access of records in a database used to prevent inconsistencies or a loss of updates. can cause deadlocks

DEADLOCK - two or more transactions are waiting for one another to give up locks

(if one person is accessing the data it locks the record so no one else can access the same record )

Question 27

Redundancy

Answer 27

process of having one or more copies of the data in physically different locations

so if its lost it can be recovered

Question 28

Composite Key

Answer 28

a key that consists of two or more attributes