Allow zero-length property

The Allow Zero Length property, when switched on, permits a field to contain a zero-length string ("") as value. This should be distinguished from the Null value, which allows fields to be blank and is permitted when the Required option is switched off.

The basic difference between a field that has a null value and one that contains a zero-length string, is that the former field contains - and has contained - absolutely nothing, that is no spaces have been entered, no deletions taken place, etc., whereas the latter may be empty to the eye but in fact has at one time contained data, even though it has since been deleted.

Hence, as you would expect, the two types of formatting cause fields to behave in different ways. Likewise, the various format combinations, using both the Required property and the Allow Zero Length property, also have different effects, as shown below:

See also:

Required property