Using Slidy

The slides for this class are HTML files which both validate as HTML 5 and pass the WAVE Accessibility Checker.
They are made to look like slides using a Javascript called Slidy.
The following keystrokes do useful things in Slidy:
- h - help (see all the commands)
- f - fullscreen (gets rid of the links at the bottom of the window
- space - advance a slide
- left/right arrows - forward or back a slide
- up/down arrows - scroll within a slide
- a - show all slides at once for printing
- u - up to the list of lectures

Introduction

Databases are now commonly used in banking, reservation systems, inventory management, universities, the web, etc.
But what is a database?
For us, a database is a collection of related data.
Data for us is a collection of known facts with some explicit meaning.
For example, you might have collections of facts about Employees, music files, etc.

A database represents some aspect of the real world (a miniworld) which is called the universe of discourse. (Say bank account info) Changes in the information are reflected in the database.
A database is a logically coherent collection of data --- A random assortment of data collected together is not a database.
A database has an intended purpose, an intended group of users, and some preconceived uses. (For example, manage amounts of money in people's accounts in a bank.)

Database Management Systems (DBMS's) are collections of programs that enable users to create, maintain, and access a database:
- To create a database involves tools for defining the data types, structures, constraints on the data and then populating it with data.
  - A DBMS provides tools for constructing the database by having programs to create the data structures for the storage of data in it using a Data Definition Language (DDL).
  - It also provides tools/programs to populate these structure and to manipulate data that has been previously stored. These tools are usually used via a Data Manipulation Language (DML).
- To share and provide access to a database, a DBMS has provides facilities to allow multiple users to obtain and manipulate stored data while ensuring data integrity.
  - A query language is implemented by the DBMS to allow users to ask questions about what data is stored in the database.
  - The DBMS often also implements an access control system to control who has access to what data in the database.
- To maintain a database involves protecting the data for long periods of time. This involves protecting against software or hardware malfunctions as well as to protect the data from malicious or clumsy users.

A database can often be represented as a sequence of named tables:
Student

Name StudentID Class Major

Brown 8 2 CS

Smith 17 1 MATH

Course

CourseName CourseID Credits Dept

Intro CS 46 3 CS

Discrete Math 42 3 MATH

Grade

StudentID CourseID Grade

8 46 A

8 42 A-

17 42 C
Columns in these tables are often called fields or attributes and often have names indicating what a value in this column represents. For example, StudentID in the Student table above.
Notice that data in a given column has a fixed datatype. For example, StudentID above is an integer.
Rows represent an entity with a given set of values for each of the columns. For example, a row in the Student tale represents the properties of a particular student such as that student's name, etc.

Name	StudentID	Class	Major
Brown	8	2	CS
Smith	17	1	MATH

CourseName	CourseID	Credits	Dept
Intro CS	46	3	CS
Discrete Math	42	3	MATH