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Flashcards in Databases Deck (20):
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Define the word database

A database is a structured collection of data

1

What's a database management system?

A database management system is a software system that enables the management of a database. E.g access, SQL, ORACLE

2

What's a data model

A method of describing the data, it's stucture.

3

What's an entity

An entity is an object/person/event about which data is recorded

4

What's a relationship?

A relationship is an association or link between two entities

5

What are names for a row?

A record or a tuple

6

What are other names for a column

Field and attribute

7

What is entity occurrence

The details of one instance of the entity

8

What's a primary key

An unique attribute which uniquely identify a tuple

9

Relational database is?

A collection of tables

10

What's composite key

A combination of attributes that uniquely identify a tuple

11

What's a foreign key?

An attribute in one table that is a primary key in another table

12

What is meant by normalised entities

A set of entities that contain no useless/redundant data

13

What's normalisation

A technique used to produce a set of normalised entities

14

What's 1NF

Table have primary key and there's no repeating groups of attributes (atomic values)

15

What's 2NF

Must be 1NF and contain no partial key dependencies - where the values of the attributes are all independent on the primary key

16

What's 3NF

Table is in third normal from if it is in 2NF and where no attributes are predictable because of any other attributes

17

What does SQL stands for?

Structured query language

18

Why is 3NF important?

It improves consistency
No unnecessarily repeated data
Eliminate update/insertion/deletion anomalies

19

What does 3NF means

Every attribute is dependent on the key, the whole key and nothing but the key.