formate check
Some things are always entered in the same format.
Think about postcode, it always has a letter, letter, number, number, number, letter and letter e.g. CV43 9PB. There may be the odd occasion where it differs slightly e.g. a Birmingham postcode B19 8WR, but the letters and numbers are still in the same order.
A picture or format check can be set up to make sure that you can only put letters where letters should be and numbers where numbers should be.
type check
Sometimes you only want data of a certain type entered into a 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 and you would prevent anyone trying to enter ‘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.
