An Introduction to Databases

What is a Database?

A database is an application used to collect, store, protect, and retrieve information. They generally provide:

• A way to create a schema (database layout)
• A way to retrieve information through a programming language (generally a 4GL and usually SQL [Structure Query Language])
• A way to protect the data through password protection (generally)
• A way to update and delete information

What Databases Do

Databases may also provide the following functions and services:

• Fast retrieval of information
• Visual interface to the data and schema
• Way to backup and restore data
• A way to undo several previous steps if one step fails along the way
• Create interdependencies upon/among the data and data types
• Allow multiple computers to "cluster" to act as a single database server
• Allow data to be split among several databases
• A way to import and export data

Popular Databases

There are several database applications ranging from small to large:

• Microsoft Access (small)
• MySQL (medium)
• IBM DB2
• Oracle
• Microsoft SQL Server

Most current databases are Relational Databases - They show how data is related to other data. Consider the example of a Video Rental Store. Videos relate to Customers (because they check them out), but also to Actors, Directors, and Publisher/Distributors. Likewise videos can be within categories (Action/Drama/Musical, etc.). We group the information into tables like Video, assigning each entry into the table (row or record) descriptive attributes (called fields) (like run time, rating, format).

Additional records for the actors would most likely be in another table. They would have fields like, name, date of birth, date of death (if applicable), and biography.