Once you collected some or all of your data you will need to enter it into your system.
It is at this point where many different types of errors can occur, coining the phrase Garbage In, Garbage Out (GIGO). Basically if you enter data which contains mistakes and errors then no matter how thorough or clever your queries are you will always get second rate, error laden results.
To date there is no 100% guaranteed foolproof method for entering data into a system which is completely error free. However there are techniques that you can use to help you reduce the errors to a minimum.
Two of these techniques are called Validation and Verification. We will be looking in more detail at them over the next few pages.