Lecture 1: Introduction to Relational Databases


Databases:
      Schema (rules about the data) + Database instance (actual data)

Database Management Systems (DBMS): a tool to manage data

      Postgresql/Oracle/SQLLite/etc

Stable storage
Data manipulation/querying
Transaction management

Relational Databases - stores a set of relations

A relation is a class of objects we want to store information about

Relation Name
Attributes
   - Domain of possible values


1. A relation stores a set of tuples
                   ----
2. Each attribute in a relation is a simple value

3. Each relations has one or more keys:

   A key is a minimal set of attributes such that no two tuples can
   have the same value for the key


Data model:
Relation: Book
Attributes:
     Title: string
     Author: string*
     NumberofPages: int
     YearPublished: int
     PublisherName: string*
     Genre: string*
     SeriesName: string
     Dewey#: string
     ISBN13: number(13)


Book           Title             Author                  Genre
----------------------------------------------------------------
               DBS Systems       Hector Garcia-Molina    Textbook
               DBS Systems       Hector Garcia-Molina    Science
               DBS Systems       Jennifer Widom          Textbook
               DBS Systems       Jennifer Widom          Science
               DBS Systems       Jeff Ullman             Textbook
               DBS Systems       Jeff Ullman             Science

---------

Relation:

StudentsInClass(Name, Major, RIN)

Database instance (tuples)

StudentsInClass      Name     Major    RIN
------------------------------------
                     River     CSCI    1
                     Mountain  ECSE    2
                     Rain      CSCI    3
                     Cloud     GSAS    4
		     Sunshine  PHL     5

It is true that (River, CSCI) is a StudentsInClass