Unit 3 : Data Model Flashcards
1
Q
What is entity?
A
- Anything about which data are collected and stored
- Example : In a school database, students, teachers, and courses could all be considered entities.
2
Q
What is attribute?
A
- A characteristic of an entity
( Column inside like Student table - name, studentID , address )
3
Q
What is relationship?
A
- Association among entities
4
Q
List out the relationship types ( 3 )
A
- One-to-many ( 1 : M ) relationship
- Many-to-many ( M : N or M : M ) relationship
- One-to-one ( 1: 1 ) relationship
5
Q
What is constraint?
A
- A restriction placed on the data
- IS NULL, NOT NULL, UNIQUE, CHECK
6
Q
List out examples for one-to-many relationship
A
- 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
7
Q
List out the example for many-to-many relationship
A
- 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
8
Q
List out the examples for one-to-one relationship
A
- 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
9
Q
What are the sources of business rules? ( 5 )
A
- Company managers
- Policy makers
- Department managers
- Written documentation
- Procedures
- Standards
- Operations Manuals
- Direct interviews with end users
10
Q
Who invented the relational model?
A
- Codd ( IBM ) in 1970
11
Q
List out 4 of the evolution of data models
A
- Hierarchical
- Network
- Relational
- Entity Relationship
12
Q
What does relational model consists? ( 12 ）
A
- Table
- Relational Diagram
- Keys ( Primary Key )
- Relationship ( one-to-many )
- Normalization ( Process of organizing data in a database to reduce redundancy and improve data integrity )
- Contraints ( NOT NULL , UNIQUE , CHECK )
- Indexes
- SQL ( Strutured Query Language)
- Data Integrity
- Views
- Stored Procedures and Triggers
- Transactions
* Use in MySQL
13
Q
What does table consists?
A
- Consist a series of row and column intersections
14
Q
What is data model?
A
- It is a relatively simple representations, usually graphical, of complex real-world data structures
- ERD is one of the data model
15
Q
Why are data models important in database design ?
A
- It facilitate interaction among the designer, the applications programmer, and the end user
16
Q
How data models help end users?
A
- It provides differents views and needs for data for end-users
17
Q
How entities are used in database? ( 2 )
A
- Tables
- Relationship ( Customer table have a relationship between Order table )
18
Q
What is instances?
A
- 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
19
Q
Why should we learn business rules in database?
A
- To know the design and operation of databases within an organization
20
Q
What are business rules ? ( Characteristics )
A
- It was a brief, precise, and unambiguous descriptions of policies, procedures, or principles within a specific organization
21
Q
What types of organizations do business rules apply? ( Characteristics )
A
- Apply to any organization that stores and uses data to generate information ( Characteristics )
22
Q
What do business rules describe within an organization? ( Characteristics )
A
1.Describe the operations that help to create and enforce actions within the organization’’s environment
23
Q
Is what form must business rules be rendered ? ( Characteristics )
A
- Must be rendered in writing
24
Q
How often should business rules be updated? ( Characteristics )
A
- Must be kept up to date
25
Can business rules originate outside of the organization? ( Characteristics )
1. Yes
26
What are the 2 key characteristics of business rules in terms of undertanding and dissemination?
1. Must be easy to understand and widely disseminated
27
What aspect of data do business rules describe as viewed by the company? ( Characteristics )
1. Business rules describe the characteristics of the data as viewed by the company.
28
How to translate Business Rules into Database Concepts? ( 3 )
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 )
29
What concepts that database system integrates? ( 2 )
1. The Relational Models
2. The Entity Relationship Model
30
What is the key concepts in the relational models ( 5 )
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.
31
What is the key concepts in the entity relationship models ( 4 )
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.
32
List out the symbols used to represent one and many in the entity relationship model ( 2 )
1. - ||
2. ||< ( Have a - inside < )
33
Which model is widely accepted and adapted graphical tool for data modeling?
1. The entity relationship model
34
Who introduced the entity relationship model
1. Chen
35
What is diamond shape in the entity relationship model?
1. To connect related entities through a relationship line
36
What does relational table resembles?
1. A file
37
Which model is purely logical structure? And why
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
