Use the IS DISTINCT FROM and IS NOT DISTINCT FROM search conditions as comparison operators.
expression1 IS [ NOT ] DISTINCT FROM expression2
The IS DISTINCT FROM and IS NOT DISTINCT FROM search conditions are sargable and evaluate to TRUE or FALSE.
expression1 = expression2 OR ( expression1 IS NULL AND expression2 IS NULL )
The IS DISTINCT FROM syntax reverses the meaning. That is, IS DISTINCT FROM evaluates to TRUE if expression1 is not equal to expression2, and at least one of the expressions is not NULL. This is equivalent to the following:
NOT( expression1 = expression2 OR ( expression1 IS NULL AND expression2 IS NULL ))