Sql 选择一个同名列标题并水平显示数据

我有两张桌子：

1-合同

    contracts_id  |  subject_contract  
    001           |  name              
    002           |  name                         

2-U文件

    contracts_id  |  file_data
    001           |  1image <varbinary(MAX)>
    002           |  1image <varbinary(MAX)>
    001           |  2image <varbinary(MAX)>
    002           |  2image <varbinary(MAX)>

我试试这个

SELECT Contracts.[contracts_id]  
      ,Contracts.[subject_contract]
      ,contracts_files.[filedata]


  FROM Contracts , contracts_files

  where contracts_files.contracts_id = Contracts.contracts_id

  AND Contracts.contracts_id=' 001 '

但结果是：

contracts_id  |  subject_contract  |  file_data  
    001       |  name              |  1image  
    001       |  name              |  2image    

---

那么，我如何使用“FOR LOOP”或“CASE”创建它呢？

您可以使用pivot，如下所示：

Select * from (
    SELECT c.[contracts_id]  
          ,c.[subject_contract]
          ,cf.[filedata]
          ,RN = Row_Number() over (partition by c.[Contracts_id] order by c.[contracts_id])
      FROM Contracts c join contracts_files cf
      ON cf.contracts_id = c.contracts_id
      ) a
      pivot (max(filedata) for RN in ([1],[2]) ) p

---

如果您不喜欢pivot，请使用旧的case方法（当某个变量=1）然后（某个值）。如果when不起作用，则使用null，MAX（）将不会返回null。突出显示内部查询并运行该查询，以查看数据在转换过程中的外观

SELECT
  contracts_id,
  subject_contract,
  MAX(CASE WHEN rown = 1 then file_data end) as file1,
  MAX(CASE WHEN rown = 2 then file_data end) as file2

FROM 
  (SELECT c.contracts_id, subject_contract, file_data, row_number() over (partition by c.[Contracts_id] order by c.[contracts_id]) as rown FROM contracts c INNER JOIN contracts_files cf ON cf.contracts_id = c.contracts_id) a
GROUP BY
  contracts_id, 
  subject_contract

---

感谢您的回复：但是，'pivot（max（filedata）for RN in（[1]，[2]）p'中出现了一些错误，我想它应该是别名。。。我更新了，你现在能检查一下吗，有什么错误吗？那么，你要求使用案例的解决方案，然后接受一个不使用它的答案？

SELECT
  contracts_id,
  subject_contract,
  MAX(CASE WHEN rown = 1 then file_data end) as file1,
  MAX(CASE WHEN rown = 2 then file_data end) as file2

FROM 
  (SELECT c.contracts_id, subject_contract, file_data, row_number() over (partition by c.[Contracts_id] order by c.[contracts_id]) as rown FROM contracts c INNER JOIN contracts_files cf ON cf.contracts_id = c.contracts_id) a
GROUP BY
  contracts_id, 
  subject_contract