Question

我在SQL中有这样的表（它不是按顺序）

A B         VAL                  VAL2
---------------------------------------------   
1 1 -2.1846000000000e+02  0.0000000000000e+00
2 2 -2.1846000000000e+02  0.0000000000000e+00
3 2  6.4000000000000e+01  0.0000000000000e+00
1 2  6.4000000000000e+01  0.0000000000000e+00
2 3  6.4000000000000e+01  0.0000000000000e+00
3 3 -2.1846000000000e+02  0.0000000000000e+00
3 1  6.4000000000000e+01  0.0000000000000e+00
2 1  6.4000000000000e+01  0.0000000000000e+00
1 3  6.4000000000000e+01  0.0000000000000e+00

因此每个元组A，B代表矩阵的一个点我怎样才能将其转换为像

这样的实际矩阵

A1                      A2                      A3
--------------------------------------------------------------------
-2.1846000000000e+02    6.4000000000000e+01     6.4000000000000e+01
6.4000000000000e+01     -2.1846000000000e+02    6.4000000000000e+01
6.4000000000000e+01     6.4000000000000e+01    -2.1846000000000e+02

Answer 1

这可以使用如下查询来完成：

select
  max(case when B = 1 then VAL end) as A1,
  max(case when B = 2 then VAL end) as A2,
  max(case when B = 3 then VAL end) as A3
from
  MatrixData D
group by
  A;

要为任意大小的矩阵生成，您需要动态生成的SQL代码，如下所示：

declare @sql varchar(5000)

select @sql = coalesce(@sql + ',' + char(13) + char(10), '') +
  'max(case when B = ' + cast(B as varchar(10))
    + ' then VAL end) as A' + cast(B as varchar(10))
from
  MatrixData D
group by
  B

set @sql =
  'select
    ' + @sql + '
  from
    MatrixData D
  group by
    A;'
exec(@sql)

演示：http://www.sqlfiddle.com/#!3/7ee1e/13

Answer 2

给定表M（x，y，v）

SELECT x, [1], [2], [3], [4], ...
FROM
(SELECT x, y, v FROM M) AS s
PIVOT
(
min(v)
FOR y IN ([1], [2], [3], [4], ...)
) AS pvt
order by x

, ...表示根据需要继续播放该剧集，但不要将其留在剧本

中

演示：http://www.sqlfiddle.com/#!3/7ee1e/17（感谢mellamokb的安装脚本）

将垂直转换为水平布局sql

2 个答案: