1.7 Database Systems

Question 1

What is a database?

Answer 1

An organized set of data constructed so that it can be searched, added to, deleted from or edited.

Question 2

State 6 functions a database allows you to do.

Answer 2

1. Create and edit data structures
2. Add, Delete and modify data
3. Format the data
4. Import data from other sources
5. Use queries to search for information
6. Produce reports about data & set security

Question 3

State 2 types of databases.

Answer 3

1. Flat-file database
2. Relational database

Question 4

What is a flat file database?

Answer 4

A database that consists of a number of
tables with no link between them.

Question 5

What is a relational database?

Answer 5

A database that consists of multiple tables that contain linked data, linked using relationships.

Question 6

Give 4 advantages for a relational database.

Answer 6

1. Less data duplication than a flat file system.
2. Data consistency : Less repetition so there is also less contradictory entries.
3. Better security; Individual users can be restricted to seeing specific parts of the database.
4. Better flexibility : adding a table is easier than making changes to a large flat file.

Question 7

Give a disadvantage for a relational database.

Answer 7

For simpler sets of data, a relational database may be overkill.

Question 8

What are primary keys?

Answer 8

Unique identifiers of a record in a database.

Question 9

What are foreign keys? (2)

Answer 9

1. A primary key from one table included in another table.
2. A field that allows a link between two tables.

Question 10

What is an entity relationship diagram? (2)

Answer 10

1. A real world thing (entity) is described
   using a database table.
2. Links are used to show the type of relationship between the entities.

Question 11

What is entity-relationship modelling?

Answer 11

Taking a real world situation and representing it using an entity-relationship diagram.

Question 12

What are the three types of relationships?

Answer 12

1. One-to-one
2. One-to-many
3. Many-to-many

Question 13

Give an example of a 1-to-1 relationship.

Answer 13

Each driver has one vehicle and each vehicle is driven by only one driver.

Question 14

Give an example of a 1-to-many relationship.

Answer 14

A teacher teaches multiple classes, but each class is only ever taught by one teacher.

Question 15

Give an example of a many-to-many relationship.

Answer 15

A student can sit any number of exams, and several students sit each exam.

Question 16

State 3 advantages of providing different views in a database system.

Answer 16

1. Restricts what someone can view in the database.
2. This improves privacy of the database.
3. Can stop people from changing data in a table.

Question 17

What is data normalisation?

Answer 17

Ensuring that the database has no data redundancy and no data inconsistencies.

Question 18

What problems occurs when data isn’t normalised?

Answer 18

Data duplication (e.g. data redundancy)

Question 19

State 3 problems with a paper based system (1).

Answer 19

1. Time consuming to find client details.
2. Difficult to back up as each piece of paper will have to be copied.
3. Time consuming to amend or create client records.

Question 20

State 3 problems with a paper based system (2).

Answer 20

1. Time consuming to search for client details.
2. Can be difficult to read due to poor handwriting.
3. Can take up a lot of physical storage space.