Introduction to Databases

What is a database?

A collection of organized data

Like what?

• Phone book

• Library catalog

• Medical records

• School catalog

Notice that all of these collections of data existed before computers.

Storing Data on a Computer

Tables have records (rows) and fields (columns).

Database Management System

Computer application that is designed to store, analyze, and manipulate data.

Example databases

• Access
• Oracle
• SQLite3
• MySQL
• PostgreSQL

The Four Major Functions

• CREATE

INSERT INTO contacts (LastName, FirstName, PhoneNumber)
VALUES ("Smith", "John", "860-223-9038");

• READ

SELECT * FROM contacts;
SELECT * FROM contacts WHERE LastName="Smith"

• UPDATE

UPDATE contacts
SET PhoneNumber="392-394-9930"
WHERE LastName="Smith";

• DESTROY

DELETE FROM contacts
WHERE LastName="Smith";

In addition to the major CRUD functions, database management systems can often process data.

Databases and Rails

• What sort of data do web applications store in databases?

• How does Rails (or any web application) interact with a database?

Questions?