framework/resources/Functional/aggregates/aggregation/group_by_case/case_in_sum_c_date.sql

select count(distinct a1) from ( select SUM(case when c_date is null then 0 else 1 end) from alltypes_with_nulls group by c_date order by SUM(case when c_date is null then 0 else 1 end)) as dt(a1);