What is a NULL Value?

Hi all,

A field with a NULL value is a field with no value.
A null value is different from a zero value or a field that contains spaces.
A field with a NULL value is one that has been left blank during record creation.
Assume, there is a field in a table is optional and it is possible to insert a record without adding a value to the optional field then the field will be saved with a NULL value.

Thank you!