Databases

Question 1

What is a database

Answer 1

A structured, persistent store of data, organised so that it can be easily accessed, managed and updated

Question 2

Describe a field

Answer 2

• Stores a single piece of data
• Has a specified data type

Question 3

Define a record

Answer 3

A collection of fields composing an entry in a database

Question 4

Define a table

Answer 4

A complete set of records

Question 5

What do databases make it convenient to do

Answer 5

• Access data
• Update data
• Search for data
• Present data in a suitable way

Question 6

Define flat-file databases

Answer 6

Databases in which all data is stored in a single table

Question 7

Define relational databases

Answer 7

Consists of multiple tables linked together. Each table usually represents a ‘thing’ or an entity and the link are their relationships

Question 8

Define primary key

Answer 8

A field that has a unique value for every record in a table

Question 9

Define foreign key

Answer 9

The primary key in one table being used as a field in another table, creating a link

Question 10

Define secondary key

Answer 10

A field by which records are likely to be searched and is therefore indexed

Question 11

What is OMR

Answer 11

Optical Mark Recognition - A data input method that recognises the positions of marks made on paper

Question 12

What is OCR

Answer 12

Optical Character Recognition - A data input method that converts images of text to machine editable text

Question 13

What is a DBMS

Answer 13

Database Management System - Software used to control a database, overseeing amendments to its structure, and used to access and amend the data itself

Question 14

Examples of DBMS

Answer 14

MySQL, Microsoft Access, PostgreSQL

Question 15

What is SQL

Answer 15

Structured Query Language - A language used to find and manipulate data within a database

Question 16

What is normalisation

Answer 16

Normalisation - The process of changing the structure of a relational database to remove the potential for data redundancy

Question 17

What does atomic mean

Answer 17

A field that cannot be broken down into multiple smaller field

Question 18

What are the rules for 1NF

Answer 18

• Data in every field is atomic
• No repeating fields
• Must have a primary key

Question 19

Define composite key

Answer 19

A primary key made of two or more fields

Question 20

What are the rules for 2NF

Answer 20

• In 1NF
• Every field must only depend on all of the primary key

Question 21

What are the rules for 3NF

Answer 21

• In 2NF
• No fields must depend on any field other than the primary key

Question 22

Explain SELECT … FROM

Answer 22

Used to retrieve specified fields from a specified table

Question 23

Explain WHERE

Answer 23

Used to filter the results that are returned

Question 24

Explain LIKE

Answer 24

Used with WHERE to select fields that match a given pattern
e.g. WHERE Name LIKE ‘New %’;

Question 25

Explain DELETE

Answer 25

Used to delete records e.g DELETE FROM Customers WHERE forename = 'Jason'

Question 26

Explain INSERT

Answer 26

Adds records into a table e.g INSERT INTO Cust (forename, surname) VALUES ('Jason', 'Smith')

Question 27

Explain DROP

Answer 27

Used to delete whole tables e.g DROP TABLE Customer

Question 28

Explain JOIN

Answer 28

Used to combine information. It selects data every time it finds a match between the two specified fields eg SELECT Subject.Subject, Teacher.Teacher FROM Subject INNER JOIN Teacher ON Subject.Teacher_Code = Teacher.Teacher_Code;

Question 29

What is referential integrity

Answer 29

Guaranteeing the consistency of a database by ensuring no record points to another record that doesn't exist

Question 30

What is a transaction

Answer 30

A group of actions in a database creating a unit of work

Question 31

What is ACID

Answer 31

Atomicity, Consistency, Isolation and Durability. These are concepts that underpin database transactions

Question 32

What is atomicity

Answer 32

A change is performed or not performed. Half-finished changes must not be saved

Question 33

What is consistency

Answer 33

Databases have sets of rules that must be adhered to by all the data they contain. Transactions should never leave a database in a state where any of these rules are broken

Question 34

What is isolation

Answer 34

A running transaction must not be able to be affected by a different transaction.

Question 35

What is durability

Answer 35

Once made, transactions cannot be lost. Changes must be written to storage in order to preserve them

Question 36

What does record locking do

Answer 36

Prevents anyone accessing a record in use by another person