Sql 如何优化和提高以下代码的性能？它获取大量记录，因此性能较慢

如何优化和提高以下Sql存储过程的性能？它获取大量记录，因此导致性能低下

该列也是非聚集索引器

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
SET NOCOUNT ON
GO

-根据T从tblA中选择所有记录

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查询的执行时间应最短，并应进行优化。

您是否有关于tblA字段T的索引？而且。。。表和预期结果中大约有多少条记录？能否对存储在表中的数据应用修剪？看起来这两个查询之间的唯一区别在于顺序。如果是这样的话，当@t='ABC'然后是V END时，您可以只进行一个查询并按大小写顺序，Seq@AngelM. 是的，我在tblA字段“T”上有一个非聚集索引。有超过8k条记录，预期结果大约有7k条记录。如果您返回了几乎所有的记录，并且您的索引没有包含SELECT as中的所有字段，则根本不会使用它。但我很惊讶，它在如此小的数据量上怎么能表现得如此缓慢。您的桌子的大小（Mb）？

 ALTER PROC [dbo].[Usp_SP1]  
    @T nvarchar(50)  
    AS  

    IF @T = 'ABC'  
    BEGIN  
 SELECT   
  xyz as [XYZK],  
  COALESCE(RTRIM(LTRIM(T)),'') AS T,  
  COALESCE(RTRIM(LTRIM(V)),'')  AS V,  
  COALESCE(RTRIM(LTRIM(Des)),'') AS Des,  
  COALESCE(Seq, 0) AS Seq,  
  COALESCE(Ac,0) AS Ac,  
  COALESCE(RTRIM(LTRIM(U)),'') AS U,  
  COALESCE(Ac,0) AS Ac,
    COALESCE(L,0) AS _L,
        COALESCE(M,0) AS _M,
        COALESCE(E,0) AS _E,
        COALESCE(S,0) AS _S


 FROM tblA WITH (NOLOCK)  
 WHERE  T = @T  ORDER BY V, Seq  
END   
ELSE  
BEGIN  
 SELECT   
  xyz as [XYZK],  
  COALESCE(RTRIM(LTRIM(T)),'') AS T,  
  COALESCE(RTRIM(LTRIM(V)),'')  AS V,  
  COALESCE(RTRIM(LTRIM(Des)),'') AS Des,  
  COALESCE(Seq, 0) AS Seq,  
  COALESCE(Ac,0) AS Ac,  
  COALESCE(RTRIM(LTRIM(U)),'') AS U,  
  COALESCE(Ac,0) AS Ac,
    COALESCE(L,0) AS _L,
        COALESCE(M,0) AS _M,
        COALESCE(E,0) AS _E,
        COALESCE(S,0) AS _S


 FROM tblA WITH (NOLOCK)   
 WHERE  T = @T  ORDER BY Seq 
END

SET NOCOUNT OFF
GO