Computing - Databases

Question 1

What is a database?

Answer 1

A store that is:
Persistent (held on permanent storage)
Related (all bits of information related to each other)
Organised (stored in structured predictable way)

Question 2

In what 3 ways can a database be viewed at?

Answer 2

External
Conceptual
Physical

Question 3

What is external view?

Answer 3

This is what the user sees and is designed to be useful for a particular job

Question 4

What is conceptual view?

Answer 4

This shows how the data and tables are organised and linked

Question 5

What is physical view?

Answer 5

The code that shows how the data is actually stored

Designers and users of the database don’t see this

Question 6

What are the 2 ways that you can construct a database?

Answer 6

Flat file

Hierarchical

Question 7

What is the difference between a flat file database and a hierarchical database

Answer 7

Flat file is a single table that is set up like a spreadsheet
Hierarchical is when items are linked like branches in a tree instead of an organised table

Question 8

What is the most commonly used database language?

Answer 8

SQL

Structured query language

Question 9

What is a DBMS?

Answer 9

A database management system is a system that provides the software tools to create, maintain and interrogate a database

Question 10

What 7 things must a DBMS do?

Answer 10

Allow data sharing
Allow multiple user access
Allow multiple application to work on them
Hold only one copy of the data
Make it possible to change data without changing applications
Provide multiple views
Present different users with data in different ways

Question 11

What is the ACID test?

Answer 11

All database transactions must be:
Atomic (change is completely performed or not at all)
Consistent (must take a database from one consistent state to another)
Isolated (should not be visible to any other user or transaction until it is completed)
Durable (when a change is made, it must not be lost due to a subsequent failure)

Question 12

What is referential integrity?

Answer 12

Different applications must not cause conflicts meaning records are locked to other applications while one application is using it

Question 13

What are relational databases?

Answer 13

Database with multiple tables that are linked to reduce data redundancy

Question 14

What is data redundancy?

Answer 14

The storing of the same data in multiple locations

Question 15

What are entities?

Answer 15

Something in the real world that some data is about

Question 16

What are attributes?

Answer 16

Something that describes an entity (eg. last name)

Question 17

What is the difference between a field and a record?

Answer 17

A field is like a cell in a spreadsheet, it contains a single attribute
A record is often a row in a table, it contains all of the attributes about an entity

Question 18

What is the difference between a primary key and a foreign key?

Answer 18

A primary key is a field that is chosen to be unique for that record (usually a reference number)
A foreign key is a field that is not unique but links to a primary key in another table

Question 19

What are forms?

Answer 19

Screen designs that present only the data the user needs

Question 20

What are queries?

Answer 20

Used to link tables and extract the data required for some purpose

Question 21

What is a boolean expression?

Answer 21

A value that can be only true or false

Question 22

What are reports?

Answer 22

An output from a database due to what the user needs

An example of an output is a spreadsheet or text document

Question 23

What are modules?

Answer 23

The units of code that have been written by the user in a DBMS