Jan's Working with Databases

   Intro: Summary

A database is basically a list. The longer the list and the more information you have about each item in the list, the more useful database software is.

A database contains records which are made up of fields. Each field is a separate piece of data, like a first name or a city or a product serial number.

Records can be sorted by arranging the records in numerical or alphabetical order based on a particular field or fields. Records can be filtered to show only the records that meet certain criteria, like prices larger than $25.00 or where the postal code is 38555.

You use a query to select fields, sort them, filter them, and do calculations with them.

A calculated field combines text fields into a single block of text or uses number fields to do a numerical calculation, like a total or average.

A form lets you edit existing records and enter new records in a easier way than directly in a table. A report lets you format a print-out of data, which may have been grouped, sorted, or filtered.

A plain text database is just a text file with each record on a separate line and the fields separated by a delimiter character like a comma or a Tab. Text databases are used these days mostly to log activities like program updates, to record data that a program needs about itself, and to transfer data between different database programs.

A flat file database uses only one table for the records. A spreadsheet can be used as a flat file database IF each record is on a single row. Nearly all flat file databases have evolved into relational databases.

A relational database uses several tables that are linked together. Each table has a primary key that matches a field, called a foreign key, in the related table. By using multiple tables, data can be entered once and connected many times to other data.

A database application is a database which has been compiled so that the users are limited in what they can do to the underlying tables, queries, forms, and reports.