选择具有最大值的列名（在SQL查询中只列出一次列名）

Question

输入：

https://dbfiddle.uk/vPuEVN2v

对于每一行，我想选择具有最大值的列名称：

---

在 SQLite 中最简洁的方法是什么，其中列名仅在 SQL 查询中列出一次？

例如，在 Oracle 中是这样实现的：

select objectid, max(col_name) keep (dense_rank first order by col_val desc) max_col_name
from employment_by_industry
unpivot (
  col_val
  for col_name in (
    agr_forest_fish, mining_quarry, mfg, electric, water_sew  --cols only listed once
  )
)
group by objected

Answer 1

您可以使用

union all

取消旋转表格，并使用

row_number

在组内订购

select objectid, col_name
from (
  select objectid, row_number() over(partition by objectid order by col_val desc) rn, col_name
  from (
    select objectid, 'agr_forest_fish' col_name, agr_forest_fish col_val 
    from employment_by_industry

    union all

    select objectid, 'mining_quarry' col_name, mining_quarry
    from employment_by_industry
    ...
    ) t
)
where rn=1