将特定列转置为单行

Question

我有以下顺序的车辆路径table

Vehicle_ID	Vehicle Path
1	101
1	55
1	136
2	50
2	65
2	75
3	101
3	105
3	110
3	125

我想要如下格式的结果。

Vehicle_ID	Path1	Path2	Path3	Path4
1	101	55	136
2	50	65	75
3	101	105	110	125

我尝试了 pivot 方法，但无法得到如上所示的结果。

Answer 1

请注意，没有第三列维护路径值的实际相对顺序。假设这个顺序无关紧要，我们可以借助 ROW_NUMBER:

WITH cte AS (
    SELECT *, ROW_NUMBER() OVER (PARTITION BY Vehicle_ID
                                 ORDER BY Vehicle_ID) rn
    FROM yourTable
)

SELECT
    Vehicle_ID,
    MAX(CASE WHEN rn = 1 THEN [Vehicle Path] END) AS Path1,
    MAX(CASE WHEN rn = 2 THEN [Vehicle Path] END) AS Path2,
    MAX(CASE WHEN rn = 3 THEN [Vehicle Path] END) AS Path3,
    MAX(CASE WHEN rn = 4 THEN [Vehicle Path] END) AS Path4
FROM cte
GROUP BY
    Vehicle_ID
ORDER BY
    Vehicle_ID;

Answer 2

另一种方式，假设 SQL Server 2017 或更高版本（并且您不关心任何给定 Vehicle_ID 的第 5 行和后面的行）：

;WITH cte AS 
(
  SELECT Vehicle_ID, 
    y = '["' + STRING_AGG(Vehicle_Path, '","') + '"]'
  FROM dbo.VehicleInfo
  GROUP BY Vehicle_ID
)
SELECT Vehicle_ID, 
  Path1 = JSON_VALUE(cte.y, '$[0]'),
  Path2 = JSON_VALUE(cte.y, '$[1]'),
  Path3 = JSON_VALUE(cte.y, '$[2]'),
  Path4 = JSON_VALUE(cte.y, '$[3]')
FROM cte;

示例db<>fiddle

Answer 3

为了完整起见，PIVOT 版本应该是这样的：

SELECT p.Vehicle_ID, p.[1] AS Path1, p.[2] AS Path3, p.[3] AS Path3, p.[4] AS Path4
FROM (
  SELECT Vehicle_ID, Vehicle_Path, ROW_NUMBER() OVER (PARTITION BY Vehicle_ID ORDER BY Vehicle_ID) ix
  FROM dbo.VehicleInfo
) AS s
PIVOT (  
  AVG(Vehicle_Path)  
  FOR ix IN ([1], [2], [3], [4])
) as p;

当然，Tim Biegeleisen 的回答中提到的顺序警告也适用于此解决方案（就像任何其他解决方案一样）。

将特定列转置为单行

Transpose specific column into single row

sql

tsql

sql-server

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