is distinct operator
Applies to: 
Databricks SQL Databricks Runtime
Tests whether the arguments have different values where NULLs are considered as comparable values.
Syntax
expr1 is [not] distinct from expr2
Arguments
expr1: An expression of a comparable type.expr2: An expression of a type sharing a least common type withexpr1.
Returns
A BOOLEAN.
If both expr1 and expr2 are NULL they are considered not distinct.
If only one of expr1 and expr2 is NULL the expressions are considered distinct.
If both expr1 and expr2 are not NULL they are considered distinct if expr <> expr2.
Examples
> SELECT NULL is distinct from NULL;
false
> SELECT NULL is distinct from 5;
true
> SELECT 1 is distinct from 5;
true
> SELECT NULL is not distinct from 5;
false