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Flashcards in Chapter 6 Deck (29)
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1

three types of knowledge

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

2

attributes/ fields

columns

3

records/ tuples

rows

4

unique key

makes it possible to link different tables to each other

5

candidate keys

when multiple keys are possible

6

primary key

the most suitable key of the candidate keys

7

join-operation

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

8

First Normal Form (1NF)

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

9

Second Normal Form (2NF)

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

10

third normal form (3NF)

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

11

entities

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

12

attributes

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

13

relationships

links between different entities

14

cardinalities

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

15

one to one

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

16

one to many

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

17

many to many

multiple A entities are related to multiple B entities

18

optional entity

relationship may not occur for certain entities (O)

19

lower cardinalities

minimum number of occurences

20

upper cardinalities

maximum number of events

21

unary/recursive relationships

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

22

tenary relationships

relationships between 3 entities

23

N-ary relationships

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

24

Data definition language

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

25

data manipulation language

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

26

data control language

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

27

relational database

data is organised in one (or more) related tables

28

entity relationship model

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

29

structured query language

default language to communicate with database systems