Chapter 6

Question 1

three types of knowledge

Answer 1

1. Entity: organisation or a person
2. organisational knowledge: retain or increase knowledge when people leave or join an organisation
3. databases: permanent knowledge

Question 2

attributes/ fields

Answer 2

columns

Question 3

records/ tuples

Answer 3

rows

Question 4

unique key

Answer 4

makes it possible to link different tables to each other

Question 5

candidate keys

Answer 5

when multiple keys are possible

Question 6

primary key

Answer 6

the most suitable key of the candidate keys

Question 7

join-operation

Answer 7

action where several related tables are linked in complex SQL queries to provide as much information as possible

Question 8

First Normal Form (1NF)

Answer 8

1. only atomic values: value cannot be divided into separate forms
2. only 1 value in the domain: not several values per box

Question 9

Second Normal Form (2NF)

Answer 9

1. meets 1NF
2. if there is a composite key, there are no partial dependencies: one of the attributes cannot depend on one of the two columns instead of both

Question 10

third normal form (3NF)

Answer 10

1. meets 2NF

2. there are no transitive dependencies: there are no attributes that are only indirectly linked to the primary key

Question 11

entities

Answer 11

things that are important to an organisation and can be both immaterial and physical

Question 12

attributes

Answer 12

describe an entity and thus represent the properties of a particular entity

Question 13

relationships

Answer 13

links between different entities

Question 14

cardinalities

Answer 14

indicate how many numbers of a given entity are related to numbers from another entity

Question 15

one to one

Answer 15

one element of entity A is related to one element of entity B (|)

Question 16

one to many

Answer 16

one element of entity A is associated with multiple elements in entity B

Question 17

many to many

Answer 17

multiple A entities are related to multiple B entities

Question 18

optional entity

Answer 18

relationship may not occur for certain entities (O)

Question 19

lower cardinalities

Answer 19

minimum number of occurences

Question 20

upper cardinalities

Answer 20

maximum number of events

Question 21

unary/recursive relationships

Answer 21

relationships that an entity has with itself (film and sequel)

Question 22

tenary relationships

Answer 22

relationships between 3 entities

Question 23

N-ary relationships

Answer 23

number of entities that are connected through relationships can in theory be endless

Question 24

Data definition language

Answer 24

used to create, delete and modify databases and tables –> structure!

Question 25

data manipulation language

Answer 25

used to receive, insert or change and remove rows --> content!

Question 26

data control language

Answer 26

users- and content-management --> access (not important for the course)

Question 27

relational database

Answer 27

data is organised in one (or more) related tables

Question 28

entity relationship model

Answer 28

describes the relationship between physical or conceptual matters that are important for the preparation of the database

Question 29

structured query language

Answer 29

default language to communicate with database systems