SELECT count() FROM (SELECT number AS x FROM system.numbers LIMIT 10);

SELECT count(x) FROM (SELECT number AS x FROM system.numbers LIMIT 10);

SELECT count(x) FROM (SELECT CAST(number AS Nullable(UInt64)) AS x FROM system.numbers LIMIT 10);

SELECT count(x) FROM (SELECT nullIf(number, 5) AS x FROM system.numbers LIMIT 10);

SELECT count(NULL);