Databases

Question 1

Entity (definition)

Answer 1

Category of objects of interest to an organisation, about which data is to be recorded

Question 2

Attribute (definition)

Answer 2

One piece of data collected about the entities in a database

Question 3

Entity descriptor (definition)

Answer 3

An entity and all the attributes related to it

Question 4

Entity descriptor for a book (example)

Answer 4

Book (BOOK_ID, title, author, date of publishing)

Question 5

Entity identifier (definition)

Answer 5

The attribute responsible for uniquely identifying an entity, usually an ID number

Question 6

Primary key (definition)

Answer 6

Unique identifier of an entity in a relational database

Question 7

Secondary key (definition)

Answer 7

Set of attributes that can uniquely identify rows in a table (but not the primary key)

Question 8

Flat file database (definition)

Answer 8

Singular file, can only specify attributes for one entity at a time

Question 9

Record (definition)

Answer 9

Single item in a database

Question 10

Relational Database (definition)

Answer 10

Data is held in tables (relations) and the tables are linked by common attributes

Question 11

Explain indexing (2)

Answer 11

Index is kept of the position of each record according to its primary key Indexes may be created for secondary keys for any attribute commonly used as search criterion (e.g. title of a book). Searching this way is faster than searching sequentially

Question 12

Secondary/alternate key (definition)

Answer 12

A set of attributes other than the primary key which can be used to uniquely identify attributes

Question 13

Entity relationship (definition)

Answer 13

The correlation between two entities

Question 14

Entity relationship modelling (definition)

Answer 14

Producing a data model for describing data or information aspects of a business domain or its process requirements, in an abstract way

Question 15

Foreign key (definition)

Answer 15

Column of attributes linking two tables together (i.e. attributes appearing in more than one table)

Question 16

Composite key (definition)

Answer 16

A unique primary key composed by adding more than one field together

Question 17

Referential integrity

Answer 17

Ensuring consistency where information is not removed if it is required elsewhere in a linked database.

Question 18

One reason referential integrity is important

Answer 18

If two tables are linked, one cannot be deleted as the other needs its contents.

Question 19

Describe a one to one relationship

Answer 19

Each entity can only be linked towards one other entity

Question 20

Describe a one to many relationship

Answer 20

One entity can be associated with multiple other entities

Question 21

Many to many relationship

Answer 21

One entity can be associated with many other entities and the same applies to the other way around