Database terminology

Question 1

Define an entity

Answer 1

A single object, person, event or thing e.g customers, appointments, products about which data is to be recorded. An entity is represented with one or more database tables.

Question 2

Define an attribute

Answer 2

A specific type of data representing a particular characteristic of each data record. Also known as a field or column.

Question 3

Define a relational database

Answer 3

A database that stores records in two or more tables. Records in one table can refer to records in another table to avoid duplicating data.

Question 4

Define a flat file

Answer 4

A database with a single table.

Question 5

Define a primary key

Answer 5

An attribute that uniquely identifies every row of the table. If there is no natural attribute for a primary key, one should be introduced. The primary key is automatically indexed and cannot be blank.

Question 6

Define a composite primary key

Answer 6

Sometimes two or even more attributes are needed to uniquely define a record. These attributes form a composite key.

Question 7

Define a foreign key

Answer 7

A primary key of one table which appears in another table. By doing this relationships between the tables are formed.

Question 8

Define a secondary key

Answer 8

A field, other than the primary key, which is indexed.

Question 9

Define an index

Answer 9

A list of keys (or keywords), each of which identifies a unique record. Indices make it faster to find specific records and to sort records by the index field (the field used to identify each record).

Question 10

Define a relationship

Answer 10

A relationship exists between two tables when one table has a foreign key that references the primary key of the other table.

Question 11

What are the 3 relationship types?

Answer 11

One-to-one, one-to-many, many-to-many

Question 12

Define a record

Answer 12

A row in a database table which contains data about one instance of an entity.

Question 13

Define data integrity

Answer 13

The overall accuracy and completeness of data

Question 14

Define referential integrity

Answer 14

A foreign key must refer to an existing primary key. Referential integrity is violated when the primary key to which a foreign key refers no longer exists. A measure of the consistency of the data in a database.

Question 15

Define a query

Answer 15

A request for data or information from a database table or combination of tables.

Question 16

Define data redundancy

Answer 16

This occurs in database systems when the same piece of data exists in multiple places.

Question 17

Define normalisation

Answer 17

The process of structuring the data in a relational database according to formal rules, in order to avoid problems of data redundancy which leads to inconsistency and inaccuracy.

Question 18

Define a field

Answer 18

A part of a record that holds data of a specific type about one characteristic of the subject of the record.

Question 19

Define a table

Answer 19

A set of data items arranged using vertical columns (identifiable by name) and horizontal rows

Question 20

What are pros of flat file databases?

Answer 20

• Easy to set up - no knowledge required
• Easy to use in code
• Easy to share, e.g. email attachments

Question 21

What are cons of flat file databases?

Answer 21

• Duplication of data (data redundancy) which take more time to update
• Take up more space so more storage is required.
• Everyone can see everything (not good if some data is sensitive)
• Inefficient – have to have all fields for every record
• Can’t perform complex queries as easily