假设你没有 NULL 值，可以使用 greatest() :

select (case greatest(country_uk, country_us)
            when country_uk then 'uk' when country_us then 'us'
        end), 
       . . .

也可以使用数组：

select (select el.what
        from unnest(array['uk' as what, country_uk as val), ('us', country_us)]) el
        order by el.val desc
        limit 1
       ) as country

下面是bigquery标准sql
它在某种程度上是非常通用的-如果您有更多或不同的段和它们的名称-您只需要在大多数外部选择中反映它-在像这样的行中( MAX(IF(segment = 'SegmentName', winner, NULL)) AS SegmentName )，其余部分在内部查询中处理

# standardSQL

SELECT id,
  MAX(IF(segment = 'Country', winner, NULL)) AS Country,
  MAX(IF(segment = 'Product', winner, NULL)) AS Product,
  MAX(IF(segment = 'Lang', winner, NULL)) AS Lang
FROM (
  SELECT id, segment, ARRAY_AGG(item ORDER BY col_value DESC LIMIT 1)[OFFSET(0)] winner
  FROM `project.dataset.table` t, 
  UNNEST(ARRAY(
      SELECT AS STRUCT segment, item, SAFE_CAST(col_value AS INT64) AS col_value
      FROM UNNEST(REGEXP_EXTRACT_ALL(TO_JSON_STRING(t), r'"\w+":[^,}]+')) kv,
      UNNEST([STRUCT(SPLIT(kv,':')[OFFSET(0)] AS col_name, SPLIT(kv,':')[OFFSET(1)] AS col_value)]) nv,
      UNNEST([STRUCT(SPLIT(TRIM(col_name, '"'), '_')[OFFSET(0)] AS segment, SPLIT(TRIM(col_name, '"'), '_')[OFFSET(1)] AS item)])
      WHERE TRIM(col_name, '"') != 'id'
    )) kv
  GROUP BY id, segment
)
GROUP BY id

如果要应用于样本数据，如您的问题-输出是

Row id  Country Product Lang     
1   abc US      A       EN   
2   def UK      B       PH

注意：最近引入的execute immediate将允许您进一步概括上述解决方案，因此您甚至不必担心最外层select中的行—我将把它留给您，因为它完全超出了主要问题的范围

SELECT TOP 1 T.Col
FROM 
(
   SELECT Country_UK AS colMax,'Country_UK' Col FROM table 
    UNION ALL              
   SELECT Country_US AS colMax,'Country_US' Col FROM table 
    UNION ALL              
   SELECT Product_A AS colMax,'Product_A' Col FROM table 
    UNION ALL             
   SELECT Product_B AS colMax,'Product_B' Col FROM table 
    UNION ALL             
   SELECT Lang_EN AS colMax,'Lang_EN' Col FROM table 
) AS T 
GROUP BY T.Col 
Order by MAX(T.colMax) DESC