Question

我有一个包含N列的表：

TABLE:
TB_SAMPLE

COLUMNS:

VALUE_A
COUNT_A
VALUE_B
COUNT_B
VALUE_C
COUNT_C
VALUE_D
COUNT_D
VALUE_E
COUNT_E
VALUE_F
COUNT_F
VALUE_G
COUNT_G
VALUE_H
COUNT_H
VALUE_I
COUNT_I

我想这样回来：

'Value', 'Count'
A, 1 -- this is the first and the second column
B, 3 -- this is the third and the fourth column
C, 4 -- this is the fifth and sixth column

等等。我已尝试使用UNION ALL子句进行多次选择，但由于我返回了大量记录，因此速度并不快。有没有更好的方法来“旋转”这个表2列？

感谢。

Answer 1

也可以使用带有CROSS APPLY声明的VALUES执行此操作：

SELECT vals, counts
FROM temp t
CROSS APPLY 
(
    VALUES
        (value_a, count_a),
        (value_b, count_b),
        (value_c, count_c),
        (value_d, count_d),
        (value_e, count_e),
        (value_f, count_f),
        (value_g, count_g),
        (value_h, count_h)
) x (vals, counts);

请参阅SQL Fiddle with Demo。

这是一篇解释如何完成此操作的文章（需要注册）：

http://www.sqlservercentral.com/articles/CROSS+APPLY+VALUES+UNPIVOT/91234/

Answer 2

你可以UNPIVOT，然后PIVOT数据，它可能表现更好：

DECLARE @T TABLE 
(   VALUE_A INT, COUNT_A INT, VALUE_B INT, COUNT_B INT, VALUE_C INT, COUNT_C INT, VALUE_D INT, COUNT_D INT, VALUE_E INT, 
    COUNT_E INT, VALUE_F INT, COUNT_F INT, VALUE_G INT, COUNT_G INT, VALUE_H INT, COUNT_H INT, VALUE_I INT, COUNT_I INT
);
INSERT @T VALUES (1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1);

WITH D AS
(   SELECT  Category = SUBSTRING(B, 7, LEN(B)), [Type] = 'Value', A
    FROM    @T
            UNPIVOT 
            (   A
                FOR B IN ([VALUE_A], [VALUE_B], [VALUE_C], [VALUE_D], [VALUE_E], [VALUE_F], [VALUE_G], [VALUE_H], [VALUE_I])
            ) upvt
    UNION ALL
    SELECT  Category = SUBSTRING(B, 7, LEN(B)), [Type] = 'Count', A
    FROM    @T
            UNPIVOT 
            (   A
                FOR B IN ([COUNT_A], [COUNT_B], [COUNT_C], [COUNT_D], [COUNT_E], [COUNT_F], [COUNT_G], [COUNT_H], [COUNT_I])
            ) upvt
)
SELECT  *
FROM    D
        PIVOT
        (   SUM(A)
            FOR [Type] IN ([Value], [Count])
        ) pvt;

如果需要，您也可以通过查询列名称的系统视图来动态执行此操作。

<强>附录

刚刚意识到这可以通过连接而不是UNION和PIVOT实现，我想联接会在删除PIVOT操作时表现更好。我仍然建议测试两者，看看哪种方法最适合您的数据。

WITH Val AS
(   SELECT  Category = SUBSTRING(B, 7, LEN(B)), A
    FROM    @T
            UNPIVOT 
            (   A
                FOR B IN ([VALUE_A], [VALUE_B], [VALUE_C], [VALUE_D], [VALUE_E], [VALUE_F], [VALUE_G], [VALUE_H], [VALUE_I])
            ) upvt
), Co AS
(   SELECT  Category = SUBSTRING(B, 7, LEN(B)), A
    FROM    @T
            UNPIVOT 
            (   A
                FOR B IN ([COUNT_A], [COUNT_B], [COUNT_C], [COUNT_D], [COUNT_E], [COUNT_F], [COUNT_G], [COUNT_H], [COUNT_I])
            ) upvt
)
SELECT  val.Category,
        [Value] = val.A,
        [Count] = co.A
FROM    val
        INNER JOIN co
            ON co.Category = val.Category;

Answer 3

这是另一种方法（如果我已正确理解你的问题）

declare @table table
(
value_a varchar(10),
count_a int,
value_b varchar(10),
count_b int,
value_c varchar(10),
count_c int,
value_d varchar(10),
count_d int,
value_e varchar(10),
count_e int,
value_f varchar(10),
count_f int,
value_g varchar(10),
count_g int,
value_h varchar(10),
count_h int
)

Insert Into @table
Select  'value a',675,
        'value b',646,
        'value c',13,
        'value d',22,
        'value e',768,
        'value f',223,
        'value g',66,
        'value h',55


SELECT  vals,
        counts
FROM 
   (
    SELECT  *
   FROM @table
    ) p
UNPIVOT
   (vals FOR cols IN 
      ([value_a],[value_b],[value_c],[value_d], [value_e],[value_f],[value_g],[value_h])
)AS unpvtValues
Unpivot 
    (
        counts for counters in ([count_a],[count_b],[count_c], [count_d],[count_e],[count_f],[count_g],[count_h])
    ) as unpvtCounts
where Right(cols, 2) = right(counters, 2)

修改

如果你想使用一些动态SQL，你可以使用这个选项（这会在你的数据库中创建一个合适的表，而不是使用表变量）

create Table dbo.TempTable ( value_a varchar(10), count_a int, value_b varchar(10), count_b int, value_c varchar(10), count_c int, value_d varchar(10), count_d int, value_e varchar(10), count_e int, value_f varchar(10), count_f int, value_g varchar(10), count_g int, value_h varchar(10), count_h int ) Insert Into dbo.TempTable Select 'value a',675, 'value b',646, 'value c',13, 'value d',22, 'value e',768, 'value f',223, 'value g',66, 'value h',55 Declare @ValueCols varchar(max), @CountCols varchar(max), @sql varchar(max) Select @ValueCols = Coalesce(@ValueCols + ', ','') + '[' + Column_Name +']' From INFORMATION_SCHEMA.COLUMNS Where TABLE_NAME = 'TempTable' And COLUMN_NAME Like 'Value%' Select @CountCols = Coalesce(@CountCols + ', ','') + '[' + Column_Name +']' From INFORMATION_SCHEMA.COLUMNS Where TABLE_NAME = 'TempTable' And COLUMN_NAME Like 'Count%' Set @sql = 'SELECT vals, counts FROM ( SELECT * FROM dbo.TempTable ) p UNPIVOT (vals FOR cols IN (' + @ValueCols +') )AS unpvtValues Unpivot ( counts for counters in (' + @CountCols + ') ) as unpvtCounts where Right(cols, 2) = right(counters, 2)' Execute (@sql) drop table TempTable

sql server query - 在n列之后的pivot

3 个答案: