$structVariantType = Variant<a: Int32, b: Int32>;

$optionalData = [
    <|variantValue: Just(Variant(1, "a", $structVariantType))|>,
    <|variantValue: Nothing(OptionalType($structVariantType))|>,
    <|variantValue: Just(Variant(2, "b", $structVariantType))|>,
];

SELECT Yql::VariantItem(variantValue) AS item FROM as_table($optionalData);