下面是bigquery标准sql

# standardSQL

SELECT domain, names_count,
  samples[OFFSET(0)] AS sample_name_1,
  samples[SAFE_OFFSET(1)] AS sample_name_2,
  samples[SAFE_OFFSET(2)] AS sample_name_3,
  samples[SAFE_OFFSET(3)] AS sample_name_4,
  samples[SAFE_OFFSET(4)] AS sample_name_5
FROM (
  SELECT domain, 
    COUNT(name) names_count,
    ARRAY_AGG(name ORDER BY RAND() LIMIT 5) samples
  FROM `project.dataset.table`
  GROUP BY domain
)

可以使用窗口函数和聚合：

select
    domain,
    count(*) names_count,
    max(case when rn = 1 then name end) sample_name_1,
    max(case when rn = 2 then name end) sample_name_2,
    max(case when rn = 3 then name end) sample_name_3,
    max(case when rn = 4 then name end) sample_name_4,
    max(case when rn = 5 then name end) sample_name_5
from (
    select t.*, row_number() over(partition by domaine order by rand()) rn
    from mytable t
) t
group by domain

子查询列组 name 他也一样 domain 随机。然后，外部查询按域聚合，并使用条件聚合为每个组带来前5个随机排列的名称。