4. Type Check

When you begin to set up your new system you will choose the most appropriate data type for each field.

A type check will ensure that the correct type of data is entered into that field.

For example, in a clothes shop, dress sizes may range from 8 to 18.  A number data type would be a suitable choice for this data.  By setting the data type as number, only numbers could be entered e.g. 10, 12, 14 and you would prevent anyone trying to enter text such as ‘ten’ or ‘ten and a half’.

Some data types can perform an extra type check. 

For example, a date data type will ensure that a date you have entered can actually exist e.g. it would not allow you to enter the date 31/02/07.