Unit 3 : Data Model

Question 1

What is entity?

Answer 1

1. Anything about which data are collected and stored

• Example : In a school database, students, teachers, and courses could all be considered entities.

Question 2

What is attribute?

Answer 2

1. A characteristic of an entity
   ( Column inside like Student table - name, studentID , address )

Question 3

What is relationship?

Answer 3

1. Association among entities

Question 4

List out the relationship types ( 3 )

Answer 4

1. One-to-many ( 1 : M ) relationship
2. Many-to-many ( M : N or M : M ) relationship
3. One-to-one ( 1: 1 ) relationship

Question 5

What is constraint?

Answer 5

1. A restriction placed on the data

• IS NULL, NOT NULL, UNIQUE, CHECK

Question 6

List out examples for one-to-many relationship

Answer 6

1. One student can enroll in many courses, but each course is taught by only one instructor

• Where one entity can be associated with many instances of another entity

Question 7

List out the example for many-to-many relationship

Answer 7

1. Students can enroll in many courses, and courses can have many students

• Where many instances of one entity can be associated with many instances of another entity

Question 8

List out the examples for one-to-one relationship

Answer 8

1. A department head leads one department and that department is led by only one department head

• Where one instance of an entity is associated with exactly one instance of another entity

Question 9

What are the sources of business rules? ( 5 )

Answer 9

1. Company managers
2. Policy makers
3. Department managers
4. Written documentation
   
   • Procedures
   • Standards
   • Operations Manuals
5. Direct interviews with end users

Question 10

Who invented the relational model?

Answer 10

1. Codd ( IBM ) in 1970

Question 11

List out 4 of the evolution of data models

Answer 11

1. Hierarchical
2. Network
3. Relational
4. Entity Relationship

Question 12

What does relational model consists? ( 12 ）

Answer 12

1. Table
2. Relational Diagram
3. Keys ( Primary Key )
4. Relationship ( one-to-many )
5. Normalization ( Process of organizing data in a database to reduce redundancy and improve data integrity )
6. Contraints ( NOT NULL , UNIQUE , CHECK )
7. Indexes
8. SQL ( Strutured Query Language)
9. Data Integrity
10. Views
11. Stored Procedures and Triggers
12. Transactions
    * Use in MySQL

Question 13

What does table consists?

Answer 13

1. Consist a series of row and column intersections

Question 14

What is data model?

Answer 14

1. It is a relatively simple representations, usually graphical, of complex real-world data structures

• ERD is one of the data model

Question 15

Why are data models important in database design ?

Answer 15

1. It facilitate interaction among the designer, the applications programmer, and the end user

Question 16

How data models help end users?

Answer 16

1. It provides differents views and needs for data for end-users

Question 17

How entities are used in database? ( 2 )

Answer 17

1. Tables
2. Relationship ( Customer table have a relationship between Order table )

Question 18

What is instances?

Answer 18

1. Refers to a specific, individual example or occurrence of an entity in a database

• Example : Customer consists Name, Email, ID, which instances is the value ( row ) inside the table, which means John Smith, john@gmail.com, 13

Question 19

Why should we learn business rules in database?

Answer 19

1. To know the design and operation of databases within an organization

Question 20

What are business rules ? ( Characteristics )

Answer 20

1. It was a brief, precise, and unambiguous descriptions of policies, procedures, or principles within a specific organization

Question 21

What types of organizations do business rules apply? ( Characteristics )

Answer 21

1. Apply to any organization that stores and uses data to generate information ( Characteristics )

Question 22

What do business rules describe within an organization? ( Characteristics )

Answer 22

1.Describe the operations that help to create and enforce actions within the organization’’s environment

Question 23

Is what form must business rules be rendered ? ( Characteristics )

Answer 23

1. Must be rendered in writing

Question 24

How often should business rules be updated? ( Characteristics )

Answer 24

1. Must be kept up to date

Question 25

Can business rules originate outside of the organization? ( Characteristics )

Answer 25

1. Yes

Question 26

What are the 2 key characteristics of business rules in terms of undertanding and dissemination?

Answer 26

1. Must be easy to understand and widely disseminated

Question 27

What aspect of data do business rules describe as viewed by the company? ( Characteristics )

Answer 27

1. Business rules describe the characteristics of the data as viewed by the company.

Question 28

How to translate Business Rules into Database Concepts? ( 3 )

Answer 28

1. Nouns translate into entities - Customer , Order table 2. Verbs translate into relationships among entities - Relationship between Customer and Order table 3. Relationships are bi-directional - We can find all orders for a customer and find the customer for a given order )

Question 29

What concepts that database system integrates? ( 2 )

Answer 29

1. The Relational Models 2. The Entity Relationship Model

Question 30

What is the key concepts in the relational models ( 5 )

Answer 30

1. Tables : Represent entities. 2. Columns : Represent attributes of entities. 3. Primary Keys : Uniquely identify each row in a table. 4. Foreign Keys: Establish relationships between tables. 5. Normalization: Ensures data integrity and reduces redundancy.

Question 31

What is the key concepts in the entity relationship models ( 4 )

Answer 31

1. Entities : Objects or things about which data is collected (e.g., Customer, Order). 2. Attributes : Characteristics of entities (e.g., CustomerName, OrderDate). 3. Relationships : Associations between entities (e.g., "Customer places Order"). 4. ER Diagrams : Graphical representations of entities, attributes, and relationships, used for designing the database schema.

Question 32

List out the symbols used to represent one and many in the entity relationship model ( 2 )

Answer 32

1. - || 2. ||< ( Have a - inside < )

Question 33

Which model is widely accepted and adapted graphical tool for data modeling?

Answer 33

1. The entity relationship model

Question 34

Who introduced the entity relationship model

Answer 34

1. Chen

Question 35

What is diamond shape in the entity relationship model?

Answer 35

1. To connect related entities through a relationship line

Question 36

What does relational table resembles?

Answer 36

1. A file

Question 37

Which model is purely logical structure? And why

Answer 37

1. Relational Table 2. How data are physically stored in the database is of no concern to the user or the designer 3. This property became the source of a real database revolution