SQL：确定每行中哪个列的值最大

我有一个列ID为a、B、C、D、E的表。。。（共10个数字列）

对于每一行，我需要找出哪个列的值最大，以及该值是什么

例如，这是我桌子上的一行：

ID A B C D E F G H I J

XY5495013217

我想生成两个新列：
maxvalue，等于9，以及 maxcol，等于“C”

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除了一个庞大的IF语句之外，还有什么建议吗？

我手头没有sql处理器，但有一些类似于

select id , colName
from 
(select id, 'A' as colName, a as value union all
select id, 'B' as colName, b as value union all
select id, 'C' as colName, c as value union all
select id, 'D' as colName, d as value union all
select id, 'E' as colName, e as value union all
select id, 'F' as colName, f as value union all
select id, 'G' as colName, g as value union all
select id, 'H' as colName, h as value union all
select id, 'I' as colName, i as value union all
select id, 'J' as colName, j as value)
group by id having max(value)

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使用

unpivot

的解决方案，假设您的表名为“TestTable”：

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当有两个值具有相同的最大值时，重复行是否正常？

WITH unpivoted as 
(
    SELECT * FROM TestTable
    UNPIVOT
    (
        Val FOR Col IN (A, B, C, D, E, F, G, H, I, J)
    ) as u
),
maxvals as (
    SELECT ID, max(val) as MaxVal 
    FROM unpivoted
    GROUP BY ID
)
SELECT
    TestTable.*, 
    MaxVals.MaxVal, 
    (SELECT top 1 Col 
     FROM unpivoted 
     WHERE unpivoted.Id = TestTable.ID and Val = MaxVals.MaxVal) as MaxCol
FROM
    TestTable
    JOIN maxvals on maxvals.id = TestTable.Id