Why aren't records returned?

Question

MySQL

There is a table:
parent_id refers to id
fk-parent_id -> id
parent_id default NULL
id(int) name(string) parent_id(int)
1 name1 null
2 ​​name2 null
3 name3 1
When I make a query:
select * from table where parent_id = 1
One record is displayed - ok
select * from table where id <> 1
Two records are displayed - ok
select * from table where parent_id <> 1
Returned 0 records. Why?

Answer 1

Because there are no matching entries. Or do you think null == 0 ?