Question

我有一张包含样本数据的表格如下。

col1    col2    col3
4       6       9
7       1       5

我想得到列的索引，其值与该行的最大值匹配，如果它们相等，则忽略后者。

例如，结果应为return

3 (because col3 has maximum value 9)
1 (because col1 has maximum value 7)

请注意，列数未定义，因此我需要一般解决方案。

谢谢

Answer 1

你可以这样做：

select case 
           when col1 >= col2 and col1 >= col3 then 1
           when col2 >= col1 and col2 >= col3 then 2
           when col3 >= col1 and col3 >= col2 then 3
        end as ColIndex
from table

Answer 2

对此更通用的解决方案（即N列）是将列展开为行，然后可以应用窗口函数以获得每组列“行”的组最大值。但是，您需要为每一行提供某种键，以便可以按行方式应用最大值（以允许重新组合原始行）。我通过Guid添加代理newId()来完成此操作。请注意，这会返回每行中具有最高值的NAME列：

WITH MyTableWithRowId AS
(
    SELECT newId() AS Id, *
    FROM MyTable
),
Unpivoted AS
(
    SELECT Ndx, Id, col, ROW_NUMBER() OVER (PARTITION BY Id ORDER BY col DESC) AS Rnk
    FROM 
    MyTableWithRowId tbl
    UNPIVOT
    (
      col for Ndx in(col1, col2, col3)
    ) p
)
SELECT Ndx
FROM Unpivoted
WHERE Rnk = 1

SqlFiddle here

编辑，只需＆＃39; 1,2,3＆＃39;不是列的名称（col1，col2，col3）

根据@ Giorgi的评论，如果您真的想要每行中列的（基于一个）序号位置，您可以加入DMV，例如INFORMATION_SCHEMA.COLUMNS来查看尽管这将是IMO非常脆弱的策略。

WITH MyTableWithRowId AS
(
    SELECT newId() AS Id, col1, col2, col3
    FROM MyTable
),
TheOrdinalPositionOfColumns AS
(
    SELECT COLUMN_NAME, ORDINAL_POSITION
    FROM INFORMATION_SCHEMA.COLUMNS
    WHERE TABLE_NAME = 'MyTable'
),
Unpivoted AS
(
    SELECT Ndx, Id, col, ROW_NUMBER() OVER (PARTITION BY Id ORDER BY col DESC) AS Rnk
    FROM 
    MyTableWithRowId tbl
    UNPIVOT
    (
      col for Ndx in(col1, col2, col3)
    ) p
)
SELECT topoc.ORDINAL_POSITION AS ColumnOrdinalPosition
FROM Unpivoted
JOIN TheOrdinalPositionOfColumns topoc ON Unpivoted.Ndx = topoc.COLUMN_NAME
WHERE Rnk = 1;

Updated Fiddle with Giorgi's Column naming

Answer 3

尝试这样的事情

select 
case when col1 >= col2 and col1 >= col3 then 1
     when col2 >= col1 and col2 >= col3 then 2
  else 3 end as [index]
from myquestion_table

查看DEMO HERE

Answer 4

试试这个：

select case 
     when col1 >= col2 and col1 >= col3 then 1
     when col2 >= col1 and col2 >= col3 then 2
     else 3
     end as ind
from mytable

Answer 5

这是一个非常基本的例子，但它可能是：

select case when col1 > col2 and col1 > col3 then col1
       when col2> col3 then col2
       else col3 end as greatestColumn
   from table

Answer 6

试试这个，没有支点。

- 您可以添加N个列。

CREATE TABLE Table1
    ([id] int primary key identity(1,1),[col1] int, [col2] int, [col3] int)
;

INSERT INTO Table1
    ([col1], [col2], [col3])
VALUES
    (4, 6, 9),
    (7, 1, 5)
;

DECLARE @tempTable as table(name varchar(50),maxValue int)


DECLARE @maxColumn int
SELECT @maxColumn = max(ordinal_position)
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME = N'Table1'

DECLARE @maxRow int
SELECT @maxRow = Count(col1) FROM Table1


DECLARE @rowCounter int = 1
DECLARE @colCounter int = 1

DECLARE @columnName varchar(max)
DECLARE @colValue varchar(max)
DECLARE @q nvarchar(max)


DECLARE @maxValue int
DECLARE @ParmDefinition nvarchar(500)
DECLARE @FinalResult table (id int, columnName nvarchar(max))
DECLARE @rowId int

WHILE(@rowCounter <= @maxRow)
BEGIN
    WHILE (@colCounter <= @maxColumn)
    BEGIN

        SELECT @columnName = COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS
        WHERE TABLE_NAME = N'Table1' and ordinal_position = @colCounter

        --select @columnName,@rowCounter,@colCounter

        SELECT @q = 'select @retvalOUT =' + @columnName + ' from Table1 where id = ' + cast(@rowCounter as NVARCHAR)

        SET @ParmDefinition = N'@retvalOUT int OUTPUT';

        EXEC sp_executesql  @q,@ParmDefinition ,@retvalOUT = @maxValue OUT
        --select '@maxValue' + @maxValue

        INSERT INTO @tempTable VALUES (@columnName,@maxValue)

        SET @colCounter = @colCounter + 1
    END



SELECT @rowId = maxValue FROM @tempTable WHERE name LIKE 'id' -- Primary key column

INSERT INTO @FinalResult(id,columnName)
SELECT TOP 1 @id,name FROM @tempTable WHERE name not like 'id' ORDER BY maxvalue DESC

DELETE FROM @tempTable

--select * from @FinalResult

SET @colCounter = 1
SET @rowCounter = @rowCounter + 1
END

SELECT * FROM @FinalResult

Answer 7

这是另一个透视解决方案，它比其他透视解决方案稍短：

DECLARE @t table
(col1 int, col2 int, col3 int)
INSERT @t 
SELECT 4,8,9 union all SELECT 7,1,5 

;WITH addrownumber AS
(
  SELECT 
    rn = row_number() over (order by (select 1)),
    *
  FROM @t
)
, unpiv AS
(
  SELECT 
    rn, 
    value, 
    colname, 
    ordinalposition = row_number() over (partition by rn order by (select 1)),
    rn2 = row_number() over (partition by rn order by value DESC, rn)
  FROM addrownumber as p  
  UNPIVOT
  (value FOR colname IN           
  ([col1], [col2], [col3])) AS unpvt  
  -- since you need all columns to be mentioned in pivot, you can set up
  --  the ordinal order here, by putting in columns in the right order.
)
SELECT ordinalposition, value, colname
FROM unpiv
WHERE rn2 = 1

结果：

ordinalposition value   colname
3               9       col3
1               7       col1

SQL - 获取具有最大值

7 个答案: