Week 4 - Database Process 1

Question 1

What is a database?

Answer 1

a self-describing collection of integrated records

Question 2

What does a database contain?

Answer 2

1. tables
2. relationships among tables
3. metadata

Question 3

What do tables do?

Answer 3

represent business objects

Question 4

What are the data elements?

Answer 4

-bytes/characters
-columns/fields
-rows/records

Question 5

What is the hierarchy of data elements?

Answer 5

bytes/characters are grouped into columns/fields>grouped into rows/records>grouped into tables/files

Question 6

Where does relationships exist among different tables?

Answer 6

rows

Question 7

How are table relationship sentences structured?

Answer 7

noun, verb, noun

Question 8

What is involved in the relationships between tables via keys

Answer 8

-primary keys
-foreign keys

Question 9

What is a primary key?

Answer 9

unique identifier for each row in a table

Question 10

What is a foreign key?

Answer 10

a column of fields that are Primary Keys in other tables (establishes relationship between tables)

Question 11

Which key do all tables have?

Answer 11

Primary Keys

Question 12

What is metadata?

Answer 12

data about the data - supports the organization and management of the database

Question 13

What is data modelling also called?

Answer 13

Entity Relationship Modelling (ER) Modelling

Question 14

What notation do we use in this unit?

Answer 14

Chens notation

Question 15

What is an Entity?

Answer 15

a table in database

Question 16

What is an entity instance?

Answer 16

a row in table

Question 17

What is an attribute?

Answer 17

a column in table

Question 18

What if you don’t have a primary key?

Answer 18

data is just a spreadsheet not a database

Question 19

What is the notation for an entity?

Answer 19

-entity is placed inside a rectangle
-capital letters
-noun

Question 20

What is the notation for an attribute?

Answer 20

-attribute is placed inside an ellipse
-first letter is a capital
-use underscore between words
-primary key is underlined
-noun

Question 21

What is a relationship?

Answer 21

link between two tables

Question 22

What is the notation for a relationship?

Answer 22

-relationship is in a diamond
-continuous lines connecting to entities
-verb

Question 23

What is a relationship instance?

Answer 23

link between two table entries

Question 24

What are the three Cardinal relationships?

Answer 24

-one to many
-many to many
-one to one

Question 25

What two Cardinal relationships are used in this unit?

Answer 25

-one to many -many to many

Question 26

If we have a one to many cardinality, explain relationship using 1-department (employs) many-adviser

Answer 26

"One department can hire many advisors, Each advisor is hired by one department"

Question 27

What is the Golden Rule for modelling Relationships?

Answer 27

The primary key of the entity on the 1-side of the relationship is ALWAYS the foreign key to the entity on the M-side of the relationship

Question 28

What is an associative entity?

Answer 28

Links two entities and contains attributes unique to their relationship

Question 29

What is the primary key when you have an associative entity

Answer 29

composite primary key - combine primary keys from other tables

Question 30

How do you name an associative entity?

Answer 30

combine entity names (sometimes has unique name)

Question 31

What is the notation for an associative entity?

Answer 31

retain verb, make box around it, write name in capitals above or below box

Question 32

If we had a many to many cardinality with and associative entity in the middle named (offer) using: supplier delivers material

Answer 32

"1 supplier can supply many materials 1 material is delivered by many suppliers"

Question 33

What are the 4 steps in creating an ERD?

Answer 33

1. identify entities 2. identify business rules (find noun verb noun relationship) 3. define relationship and represent cardinality 4. identify attributes

Question 34

What is a unary reationship?

Answer 34

relationship between two different instances of an entity

Question 35

What is an example of a unary relationship?

Answer 35

when one employee supervises other employees

Question 36

What is the acronym to remember the components in an ER diagram?

Answer 36

PACER

Question 37

What does PACER stand for?

Answer 37

-Primary key -Attribute -Cardinality -Entity -Relationship