Defining Databases

A database is a structured collection of data objects [text, audio files, graphics, videos] stored in a computer system.

Traditional databases are organized by fields, records, and files.

• A field is a single piece of information
• A record is one complete set of fields
• A file is a collection of records.

For example, a telephone book is a file. It contains a list of records, each of which consists of three fields: name, address, and telephone number.

Database Queries

Data is accessed using a query language [SQL, Structured Query Language] to answer queries. The records retrieved represent the answer to queries, and are information that can be used to make decisions.

The computer program used to manage and query a database is known as a database management system (DBMS).

A typical query could be to answer questions such as, "How many cars with additional electronic options were sold in the month of March in region 4?".

To answer such a question, the database would have to store information about cars sold, electronic options, sales of each electronic option, sales date, and the region of sales.

This information is organized in a structure, described as a schema.

Schemas

The schema describes the objects that are represented in the database, and the relationships among them.

There are different ways of organizing a schema [modeling the database structure]. These are known as database models [data models].

Models

The most common models are:

• Relational Model - which represents all information in the form of multiple related tables each consisting of rows and columns. Relationships are defined by using values common to more than one table.
• Relational Object Model

Database Models

Most database systems are built around one particular data model, although many products support more than one model.

For any one logical model various physical implementations are possible, that have a significant effect on performance. For instance, the relational model allows the creation of indexes which provide fast access to rows in a table if the values of certain columns are known.

The two most common models used are:

1. Relational model
2. Object model

Other database models are used for specific purposes, and for added contextual attributes, fuzzy logic databases are employed.

NEXT: Relational Database Models

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