Database

Question 1

Managing data

Answer 1

•Data increases exponentially with time
•Multiple sources of data
•New sources of data
•Data become less current over time •Data rot
•Unstructured data
•Big data

Question 2

Data: challenges

Answer 2

1. Increase: volume
2. Sources: internal sources/ resource database
   - personal sources
   - external sources (government database)
3. Data streams
   - point of scale terminal data
   - blogs, social media RFID
   - strange media
   - Unstructured data (textual data)
   - Big data

Question 3

The database approach

Answer 3

Database is an organized collection of related information especially for rapid search and retrieval
●is managed with database management information systems (DBMS).

Question 4

Databases minimize the following problems

Answer 4

◦Data redundancy: The same data are stored in many places.
◦Data isolation: Applications cannot access data associated with other applications.
◦Data inconsistency: Various copies of the data do not agree.

Question 5

Database management systems (DBMS) maximize the following

Answer 5

● Data security: Databases must have extremely high security measures in
place to deter mistakes and attacks since data is stored in one place.
● Data integrity: Data must meet certain constraints, such as no alphabetic characters in a Social Insurance Number field.
● Data independence: Applications and data are not linked to each other (kept

Question 6

Building a database

Answer 6

Step 1: Create a data model: ER model
Step 2: Document the data model: ER diagram
Step 3: Implement the ER model in a DBMS

Question 7

ER model

Answer 7

•Data model is a diagram that represents the entities in the database and their relationships
•Entity is a person, place, thing, or event about which an organization maintains information. A record describes an entity.
•Instance is one specific, unique representation of the entity.
•Attribute is a characteristic or quality of a particular entity
•Primary key is a field that uniquely identifies a record. Note that every record MUST have a primary key.

Question 8

Relationships

Answer 8

One to one (1:1)
● One instance of an entity A is associated with at most one
instance of entity B, and vice versa

One to many (1:M)
●For one instance of entity A, there are zero, one, or many instances of entity B, but for one instance of entity B, there is only one instance of entity

Many to many (M:M)
For one instance of entity A is associated with at most one

Question 9

Relationship

Answer 9

The most common relationship is binary relationships, which refer to the association between two entities
Cardinality and modality indicate business rules

Question 10

What do cardinality and modality indicate and what are they

Answer 10

●Cardinality refers to the maximum number of times an instance in one entity can be associated with instances in the related entity.
●Modality refers to the minimum number of times an instance in one entity can be associated with instances in the related entity.

Question 11

Cardinality symbols

Answer 11

• Crow’s foot notation represents entities as boxes
• Represents relationships as lines between the boxes

On the relationship line:
- Cardinality is close to the entity box
the dash represents “one”
the crow’s foot represents “many” or “infinite“
- Modality is away from the entity box the ring represents “zero“
the dash represents “one”

Question 12

Database management systems

Answer 12

Software for creating and managing databases
◦The DBMS provides users and programmers with a systematic way to create, retrieve, update and manage data
●RDBMS
●A software system used to maintain relational databases is a
relational database management system (RDBMS)
●Microsoft Access for small business
●for large businesses, Oracle 12c, IBM DB2, SAP HANA, and Microsoft SQL Server