Database = Data Model + Data Instance + Application Logic 

Database Management System

Postgresql
IBM DB2
SQL Server
MYSQL
MariaDB

Neo4J
Excel
MangoDB
BigTable
MsAccess


Relational Database Management System
      Relational Data Model

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

Relational Data Model

Database = a set of relations
             ----
	     
A relation (table) = a set of tuples
                       ----

{A,B,C} = {B,A,C} = {A,B,C,C,C,B}

A tuple = a set of attribute/value pairs


 Students(RIN, FirstName, LastName, Major, Class, Address, DoB, Advisor, Email)

Classes(Code, Topic, Title, Instructor, Semester, Year, Section, NumStudents, Classroom, CRN)

--> 1 Rule: attributes can only simple values

Key: A set of attributes in a relation such that no two tuples can have the same value for the key,
and no subset of the attributes is a key.


Key for students?

RIN
Email

Assume RIN is a key:

Students

RIN Name     Major     Advisor
-------------------------------
1    Sibel   CSCI      Stewart
2    Rich    ECSE      Wen
1    Sibel   ARTS      Vamos

Can a student have two majors? Yes

Change key to RIN, Major


Students(RIN, FirstName, LastName, Major, Class, Address, DoB, Advisor, Email)

What is a key?

A student can have two majors.
A student can have two advisors.

Key:

RIN, Major, Advisor
Email, Major, Advisor


Classes(Code, Topic, Title, Instructor, Semester, Year, Section, NumStudents, Classroom, CRN)

Key:  Assume no cross listings and a single title, but multiple isntructors is possible

CRN, Instructor
Code, Topic, Semester, Year, Section, Instructor


StudentPhoneNumbers(RIN, PhoneNumber)

Can a student have multiple phones? Yes
Can a phone be shared by multiple students? Yes

Key: RIN, PhoneNumber