Class FAQ:
------------

. What will be covered in this class? How is the content organized?

Data modeling
Data management, SQL
Database internals

. What do I need to know in advance?

FoCs, DS, OpSys

. Do I need to install a database management system on my computer?


. What else might be good for me to learn?



Introduction to Relational Databases
Textbook, Chapter 1
--------------------------------------


Database
Relational Database


Components of DBMS


. Data model: rules about your data
. Database: data model + actual data objects

DBMS: Database Management System

- Postgresql
- MariaDB
- MySQL
- Oracle
- SQLLite
- IBM DB2
- Informix
- Access
- Sqlserver


- MangoDB
- Excel?
- DynamoDB?
- GraphQL
- Google Firebase


DBMS components:

- Storage manager
- Query and data manipulation language
- Transaction manager

    Atomic  - 
    Consistency
    Isolation
    Durability


Types of databases:

- Relational databases  ****
- Hierarchical databases
- Object oriented databases
- Graph databases
- Relational databases + object relational extensions





A relational database
-------------------------

Database = a set of relations

Data model: 

Each relation has a set of attributes

Each attribute has a domain: a set of valid values

~~~~~~~~~~~~~~~

Database: SIS

Relations: Students, Courses, Classes, Grades, FinancialInfo, Faculty

Attributes:

    Classes: Section, Course Code, Subject Code, CRN, Classroom, MaxEnrollment, Format, Semester, Year
    
    Students: First, Middle, Last, Pronouns, Preferred Name, RIN, SSN, Address, email, flex balance

Domain of an attribute: set of valid values:

Course Code: 4 digit code, Subject Code: 4 letters, CRN:5 digits
RIN: 9 digits start with 66

A database is a set of relations.

A database instance is a set of tuples in each relation such that each
tuple satisfy the data model rules.

Relations -------  Tables
Attributes  ------ Columns
Tuples    -------- Rows

--------------

Rule 1: A relation instance is a set of tuples. [[tuples are not repeated!]]

{1,1,2,3,4} == {1,2,3,4} == {2,3,4,1}


Rule 2: All attributes are simple, contain flat, atomic values.


Key of a relation: A key for a relation is a minimal set of attributes
such that no two tuples can have the same values for the key.

Students: First, Middle, Last, Pronouns, Preferred Name, RIN, SSN,
          Address, email, flex balance

          Key: RIN
	  Key: Email
	  Key: SSN

Classes: Section, Course Code, Subject Code, CRN, Classroom,
         MaxEnrollment, Format, Semester, Year
    
         Key: CRN
	 Key: Section, Course Code, Subject Code, Semester, Year


StudentHobbies(CRN, Hobby)
         Key: CRN, Hobby