Databases

Introduction

Databases are used to store, manage and report upon information. This information is stored in tables and similar to spreadsheets it is stored in columns and rows. Each column represents a different attribute and each row a different record.

Database Types

There are two main types of database:

• Flat-file
• Relational

Flat-file - ideal for small amounts of data and simple lists such as a telephone number list.

Relational - used when you require more than one table which are linked to each other.

Data Organisation

All the tables in the database require a unique name so that the Database Management System (DBMS) does not get confused.

Each column also requires a unique name for the same reason.

The table requires a column where all the fields are unique. This is referred to as the `Primary Key` and it is used for the purpose of indexing the table, making it more efficient to search and sort the data.

Table Structure

How many tables are required depends on how you break down the data requirements. One large table would be inefficient and unmanageable and too many tables becomes confusing.

Take a small Customer Sales database where you want to track all transactions with each of your customers. You may have a Customer table with their name and contact details etc and a separate table with the items you have for sale.

Relationships

By using the Primary Key of each table you can link each customer with the items they buy.

Every time Customer 1 buys one or more items we can assign the item_number from the Item table with the customer_number from the Customer table.

Real Options would be happy to help, advise or build a database to your specifications.
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