Putting it very simply a null value is empty and a not null value contains something.

A Null Character, is a control character with a value of zero.

Yes Foreign key can have null value.

A: Practically all of the bridges used to find the value of passive components uses a null signal to determine the value In reality null means the lack of a signal where it is virtually eliminated when that occurs that is the null or no signal.

Null defines the value in a banking account as zero, no value. Zero or null are used to state the same idea on banking and investment documents.