VARCHARnn is an Oracle data type that identifies the field in the data base as holding alphanumeric (characters and numbers) values with a variable length not to exceed the number indicated. For example, a field defined as VARCHAR30 may hold a value which has a length up to 30 characters long, but only actually uses as much space as needed on the disk. If the value is unspecified (length = 0) then this is known as NULL value.