"= Null" <> "is Null"?

Hi!

select * from any where is_deleted = Null

select * from any where is_deleted in (Null)

They are show 0 record.

select * from any where is_deleted is Null

It is show all records.

Some of other DBs are uses Null as Null in >=< comparisons. Is PG not? What are the rules?

Thanks: dd