按列名稱進行組查詢MSSQL

Question

我有一個具有以下架構的表

但是我需要將該信息導出到另一個表，但是我需要的結果必須是這樣的

其中計算機值必須來自列名稱之一的名稱，而所有內容都必須針對Sql Server

Answer 1

使用cross apply()與values()來取消數據透視：

  select v.Machine, v.Temperature, v.Humidity, t.Fecha
  from t
    cross apply (values ('DR673',DR673_T,DR673_H),('DR677',DR677_T,DR677_H)
      ) as v(Machine, Temperature, Humidity)

---

要基於列名稱動態生成sql，請執行以下操作：

declare @cols nvarchar(max), @sql nvarchar(max);

set @cols = stuff((
   select distinct 
      ',(''' + left(C.name,charindex('_',c.name)-1) 
      + ''','+ quotename(C.name) 
      + ','+ quotename(left(C.name,charindex('_',c.name))+'H') 
      +')'
   from sys.columns c
   where c.object_id = object_id('dbo.t')
     and c.name like '%_T'
   for xml path (''), type).value('.','nvarchar(max)')
  ,1,1,'');

set @sql = '
select v.Machine, v.Temperature, v.Humidity, t.Fecha
from t
  cross apply (values '+@cols+'
  ) as v(Machine, Temperature, Humidity)';

  select @sql as CodeGenerated;
  --exec sp_executesql @sql; /* to execute the dynamic sql */

extrester演示： http ：//rextester.com/NAOT80053

收益：

+---------------------------------------------------------------------------------------+
|                                     CodeGenerated                                     |
+---------------------------------------------------------------------------------------+
|     select v.Machine, v.Temperature, v.Humidity, t.Fecha                              |
|     from t                                                                            |
|       cross apply (values ('DR673',[DR673_T],[DR673_H]),('DR677',[DR677_T],[DR677_H]) |
|       ) as v(Machine, Temperature, Humidity)                                          |
+---------------------------------------------------------------------------------------+