Why does value="" write empty and not NULL?

Question

MySQL

As I understand it, in SQL
NULL is emptiness and it is better to write it than an empty string.
Or does it make any difference whether I will check the column for NULL or for emptiness?
It's just that there are problems with writing NULL, but writing emptiness is not difficult.

And if NULL is better, then how to write it through value?
value="NULL" - writes "NULL" as a string, not as NULL

Answer 1

NULL and an empty string are two completely different things (the exception is Oracle). NULL is the absence of any, including empty, value.