Glossary

Question 1

Data

Answer 1

Stored representations of objects and events that have meaning and importance.

Question 2

Information

Answer 2

Data that has been processed in such a way as to increase knowledge of the person who uses it.

Question 3

Database

Answer 3

An organised collection of logically related data.

Question 4

Entity

Answer 4

A person, a place, an object, an event, or a concept in the user environment about which the organisation wishes to maintain data.

Question 5

Relational Database

Answer 5

A database that represents data as a collection of tables in which all data relationships are represented by common values in related tables.

Question 6

Database Management System (DBMS)

Answer 6

A software system that is used to create, maintain, and provide controlled access to a user database.

Question 7

Entity Relationship Model

Answer 7

A logical representation of the data for an organisation or for a business area, using entities for categories of data and relationships for associations between entities.

Question 8

Entity Relationship Diagram (ERD)

Answer 8

A graphical representation of an Entity Relationship Model.

Question 9

Business Rule

Answer 9

A statement that defines or constrains some aspect of the business. It is intended to assert business structure or to control or influence the behaviour of the business.

Question 10

Identifier / Primary Key

Answer 10

An attribute (or combination of attributes) whose value distinguishes instances of an entity type.

Question 11

Foreign Key

Answer 11

An attribute in a relation that serves as the primary key of another relation in the same database.

Question 12

Schema

Answer 12

A structure that contains description of objects created by a user, such as base tables and constraints as part of a database.

Question 13

Structured Query Language (SQL)

Answer 13

SQL is the language used by all DBMS’s.

Question 14

Entity Instance

Answer 14

A single occurrence of an entity type.

Question 15

Referential Integrity Constraint

Answer 15

A rule that states that either each foreign key value must match a primary key value in another relation or the foreign key value must be null.

Question 16

Cardinality Constraint

Answer 16

A rule that specifies the number of instances of one entity that can (or must) be associated with each instance of another entity.

Question 17

Minimum Cardinality

Answer 17

The minimum number of instances of one entity that may be associated with each instance of another entity.

Question 18

Maximum Cardinality

Answer 18

The maximum number of instances of one entity that may be associated with each instance of another entity.

Question 19

Data Definition Language (DDL)

Answer 19

Commands used to define a database, including those for creating, altering, and dropping tables and establishing constraints.

Question 20

Data Manipulation Language (DML)

Answer 20

Commands used to maintain and query a database, including those for updating, inserting, modifying, and querying data.

Question 21

NULL

Answer 21

A value that may be assigned to an attribute when no other value applies or when the applicable value is unknown.

Question 22

Data Redundancy

Answer 22

This is a condition created within a database or data storage technology in which the same piece of data is held in two separate places. Relations that have redundant data have data anomalies, which are classified as:

1. Insertion anomalies
2. Deletion anomalies
3. Update/Modification anomalies

Question 23

Anomaly

Answer 23

An error or inconsistency that may result when a user attempts to update a table that contains redundant data.

Question 24

Constraint

Answer 24

A rule that cannot be violated by database user.

Question 25

Strong Entity Type

Answer 25

An entity that exists independently of other entity types.

Question 26

Weak Entity Type

Answer 26

An entity type whose existence depends on some other entity type.

Question 27

Relationship Type

Answer 27

A meaningful association between (or among) entity types.

Question 28

NOT NULL Constraint

Answer 28

The NOT NULL constraint enforces a column to NOT accept NULL values.

Question 29

UNIQUE Constraint

Answer 29

The UNIQUE constraint ensures that all values in a column are different.

Question 30

CHECK Constraint

Answer 30

The CHECK constraint is used to limit the value range that can be placed in a column.

Question 31

Multi Valued Attribute

Answer 31

An attribute that may take on more than one value for a given entity (or relationship) instance.

Question 32

SQL Sub-Queries

Answer 32

A sub-query is a SQL query nested inside a larger query.

Question 33

SQL Views

Answer 33

In SQL, a view is a virtual table based on the result-set of an SQL statement. A view contains rows and columns, just like a real table. The fields in a view are fields from one or more real tables in the database.

Question 34

Ternary Relationship

Answer 34

A simultaneous relationship among the instances of three entity types.