SQL查询从多个列获取多个最大值

Question

I am trying to figure out how to pull multiple max values from multiple columns. Here is some sample data:

DATE | A | B | C

4/4/2011 | 64.4 | 62.1 | 33.3

4/5/2011 | 34.6 | 33.5 | 32.3

4/6/2011 | 33.1 | 49.4 | 32.1

4/7/2011 | 55.2 | 32.8 | 33.5

4/8/2011 | 31.2 | 50.1 | 30.4

4/9/2011 | 31.7 | 31.1 | 30.4

I want the top 5 so:

4/4/2011 | 64.4

4/4/2011 | 62.1

4/7/2011 | 55.2

4/8/2011 | 50.1

4/6/2011 | 49.4

Thanks

Answer 1

How about:

SELECT TOP 5 Date, Val 
FROM (SELECT Date, A as Val FROM T
      UNION ALL
      SELECT Date, B FROM T
      UNION ALL
      SELECT DATE, C FROM T
) AS x
ORDER BY x.Val DESC

Answer 2

You could use UNPIVOT then order by the column value then take only the top 5.

Like This......

CREATE TABLE #Data 
(
    [Date] DATE,
    A  FLOAT,
    B  FLOAT,
    C  FLOAT
)

INSERT INTO 
    #Data
SELECT '4/4/2011' AS Date, '64.4' AS A, '62.1' AS B, '33.3' AS C
UNION SELECT '4/5/2011' AS Date, '34.6' AS A, '33.5' AS B, '32.3' AS C
UNION SELECT '4/6/2011' AS Date, '33.1' AS A, '49.4' AS B, '32.1' AS C
UNION SELECT '4/7/2011' AS Date, '55.2' AS A, '32.8' AS B, '33.5' AS C
UNION SELECT '4/8/2011' AS Date, '31.2' AS A, '50.1' AS B, '30.4' AS C
UNION SELECT '4/9/2011' AS Date, '31.7' AS A, '31.1' AS B, '30.4' AS C

SELECT * FROM #Data

SELECT TOP 5
    [Date],
    [Type],
    [Value]
FROM
(
    SELECT  
        [Date],
        [A],
        [B],
        [C]
    FROM
        #Data 
)pvt
UNPIVOT
(
    [Value] FOR [Type] IN
    ( [A],[B],[C])
)AS unpvt
ORDER BY
    [Value] DESC

DROP TABLE #Data

Answer 3

One thing that you do not tell us is if you want unique results or allow duplicates.

GilM's answer would allow duplicates because he uses UNION ALL.

UNION would return unique results.