Introduction to Database programs

Small to medium companies usually have one database for all their needs; larger companies may have several databases, each for a different use.

PC databases generally include the following components to make this possible, each of which is described below:

Tables,
Forms, 
Queries, and 
Reports

Tables

Tables are the heart of a database because they are the containers that actually store the information. Each type of information is stored in a different table. For example, a typical company might have separate tables for Customers, Orders, Inventory, etc.

	Tables in a database

Within a table, fields are set up to store the information appropriate for that table. For example, the "Customer" table normally include fields for Company Name, Street Address, PO Box, City, State, Zip Code, etc.

Fields have different data types - for example, dates, currency, text and number. This allows the database to do checks to make sure the information meets general rules (for example, it won't let you put the date "2/31/03" into a date field). This also allows the use of special "functions", such as the ability to subtract one date from another to tell how many days are between them.

Forms (commonly called "screens")

Usually databases allow you to "input" new information into a table in "spreadsheet" format (rows and columns, like the example below).

	Data entry into a table without a screen, or "form"

This format isn't very easy on the eyes. Most PC database programs have tools that make the creation of data entry screens fairly easy. Following is an example of "form" that allows a user to do data entry and data maintenance for the same table:

 

	Data entry "Form"
This form took only a couple of minutes to create using Microsoft Access. It automatically gives you the ability to: Insert new customers, Edit existing customers, and Delete existing customers

Click here for details on how easy it is to create a data-entry form using Access.

Queries

A query is a request sent to the database to get specific information from it, usually for a specialized use such as:

Total sales for each of the last six months, or
Customers who haven't ordered anything in the last three months, or
Names and phone numbers of all the customers in Connecticut

Following are some sample queries: 

     Get certain fields only, all customers

	Sample Query	Explanation
	SELECT CompanyName, Phone FROM Customers	List the Name and Phone# for all Customers

     Get only certain customers

	Sample Query	Explanation
	SELECT * FROM Customers WHERE State="CT"	List all information for Customers who have an office in Connecticut

     Display in alphabetical order

	Sample Query	Explanation
	SELECT * FROM Customers ORDER BY CompanyName	List all information for Customers List alphabetically by Company Name

Reports

Queries return information in the spreadsheet format (rows and columns), which isn't that easy to read.  A "report" lets you store instructions as to how to print the "raw" information so it's easy to read and understand, and includes options such as:

Select Run a query to select the desired information Format Set size, font, color, spacing, column width Display order List alphabetically, in date order, by increasing or decreasing quantity, etc. Groups Put information in groups - for example, all the orders for one customer, or all the customers in one state Totals Calculate and print totals for one row of information, a group, and/or the entire report Headings Print descriptive names for each column, group, the report overall, etc.