Привет! Получаю ошибку DB::Exception: Different order of columns in UNION subquery:

countMerge(count_events) and country, countMerge(count_events).
когда пытаюсь сделать так
with a as
((
SELECT
country
,countMerge(count_events)
FROM table1
GROUP BY country

except
SELECT
country
,countMerge(count_events)
FROM table2
GROUP BY country
)
union all
(
SELECT
country
,countMerge(count_events)
FROM table2
GROUP BY country

except

SELECT
country
,countMerge(count_events)
FROM table1
GROUP BY country

))
select count() from a;


но при этом вот такой (логически эквивалентный вариант) отрабатывает без ошибок:

with a as
(
SELECT
country
,countMerge(count_events)
FROM table1
GROUP BY country

except
SELECT
country
,countMerge(count_events)
FROM table2
GROUP BY country
)
, b as
(
SELECT
country
,countMerge(count_events)
FROM table2
GROUP BY country

except

SELECT
country
,countMerge(count_events)
FROM table1
GROUP BY country

)
SELECT count()
FROM
(
SELECT *
FROM a
UNION ALL
SELECT *
FROM b
)

В чем может быть причина?

при выставлении set allow_experimental_analyzer=1 - ошибка уходит