Sql aGohil此查询生成的行的顺序与您的相同。如果要对CreatedDt进行降序排序，请在ORDER BY CreatedDt@DevendraGohil之后插入desc：我更新了答案，以说明如何为主要排序标准指定降序。（对不起，你的帖子中没有提到这一点。）

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aGohil此查询生成的行的顺序与您的相同。如果要对CreatedDt进行降序排序，请在

ORDER BY CreatedDt

@DevendraGohil之后插入

desc

：我更新了答案，以说明如何为主要排序标准指定降序。（对不起，你的帖子中没有提到这一点。）

SELECT CreatedDt as 'Date/Time' , null AS [Alert_Type] FROM TblA
union  
SELECT CreatedDt as 'Date/Time' , null AS [Alert_Type] FROM TblB
union  
SELECT CreatedDt as 'Date/Time' , null AS [Alert_Type] FROM TblC
union
SELECT CreatedDt as 'Date/Time' , Alert_Type FROM TblD
ORDER BY CreatedDt, ISNULL (Alert_Type,'aa') DESC

ORDER BY items must appear in the select list if the statement contains a UNION, INTERSECT or EXCEPT operator.

ORDER BY  CASE WHEN column_name IS NULL
               THEN 1
               ELSE 0
          END ASC --, other sorts
                  -- in these case NULL columns should be on the bottom part

select * from (

SELECT CreatedDt as 'Date/Time' , null AS [Alert_Type] FROM TblA
union  
SELECT CreatedDt as 'Date/Time' , null AS [Alert_Type] FROM TblB
union  
SELECT CreatedDt as 'Date/Time' , null AS [Alert_Type] FROM TblC
union
SELECT CreatedDt as 'Date/Time' , Alert_Type FROM TblD)a
order by CreatedDt desc, 
         case when Alert_Type is null then 0 else 1 end

SELECT CreatedDt as 'Date/Time' , 'aa' AS [Alert_Type] FROM TblA
union  
SELECT CreatedDt as 'Date/Time' , 'aa' AS [Alert_Type] FROM TblB
union  
SELECT CreatedDt as 'Date/Time' , 'aa' AS [Alert_Type] FROM TblC
union
SELECT CreatedDt as 'Date/Time' , Alert_Type FROM TblD
ORDER BY CreatedDt DESC, Alert_Type DESC