Your Access database training doesn't stop after one course. Further courses introduce new techniques, but nothing substitutes for experience. To save you headaches, here are some common mistakes to avoid.



Making a field the wrong data type

Your Access database training showed you the different data types but sometimes the obvious type is not the correct one. A telephone number is made up of numbers so should be a numeric field, right? Wrong. Numeric fields are for values that might be used in calculations. A telephone number field should actually be assigned a text data type.

Using one table for all data

Many people new to Access database training have trouble embracing the concepts of a relational database. For example, an invoice contains customer information, the list of products purchased, and the invoice information such as date of purchase. New users picture an invoice in their heads and try to fit all that information into one table.

This creates redundant information and wasted space. Customer and product information are repeated for every invoice rather than just entered once.

Advanced Access database training illustrates that the correct way to accomplish this is by creating three tables: invoices, customers, and products. Each item has a unique identifier, such as InvoiceID, CustomerID, and ProductID respectively. Each item is entered only once but the invoice objects tie them all together.

Putting too much data into a field

Another error made by new users is to combine too much information into one field. For example a car mechanic might put the year, make, and model of customer cars all into one field. This becomes a problem if he wants to find all vehicles made before 1995 or all Subaru owners. Your Access database training shows how easy it is to combine fields on an invoice or report, so always ask yourself if this information might be better separated into different fields.

Using default field sizes

You may have learned in your Access database training that text fields have a default length of 50. Consider how long a field needs to be and set the field length accordingly rather than taking the default. If your customer ID is 8 characters long, then allotting 50 characters is just wasteful. It may not seem like much but over many fields in many customer records your database will become huge and slow to load.

A similar concern applies to number fields. Number fields default to long integer which, as you may have learned in your Access database training, means it holds no decimal places and holds values in the approximate range of +/- 2,000,000. If you are storing smaller numbers, an integer or even a byte value will save space. If you need to store decimal places, then a single or double is more appropriate.