Null value in Database

Question

Null value means

1. No value
2. Inapplicable,unassigned, unknown, or unavailable

Which is true?

Answer 1

It's all about the context in which it's used. A null means there is no value but the reason for this will depend on the domain in which it is being used. In many cases the items you've listed are all valid uses of a null.

Answer 2

It can mean any of those things (and it is not always obvious which), which is one argument against using nulls at all.

See: http://en.wikipedia.org/wiki/Null_(SQL)#Controversy