NULL and null predicates

NULL represents a missing value. Test it with IS NULL or IS NOT NULL.

RETURN NULL IS NULL AS missing, NULL = NULL AS equality;

missing is true and equality is null. Missing graph properties and absent optional bindings can produce nulls. A property on a null element evaluates to null.

The engine retains typed nulls where context or a declared parameter provides a type. Null-only values are compatible with supported typed expressions; arbitrary incompatible families are still rejected.

COALESCE supplies a fallback. PROPERTY_EXISTS checks whether a particular element property has a non-null value.