Question

我有一个每秒返回大量数据的SP，并以网格显示。我现在正在尝试减少带宽并考虑仅返回当前显示在网格中的列。

这当然是简化和最小化的，但基本上我所拥有的是以下SP：

SELECT
[Animals].[AnimalID] AS [AnimalID],
[Animals].[name] AS [AnimalName],
[Foods].[DisplayName] AS [Food],
[Animals].[Age] AS [AnimalAge],
[Animals].[AmountOfFood] AS [AmountOfFood]

我目前正在尝试传递当前在网格上显示的字段名称（@fields）的TVP，并仅返回所需的字段：

SELECT
[Animals].[AnimalID] AS [AnimalID],
[Animals].[name] AS [AnimalName],
CASE 
    WHEN ('Food' in (select * from @fields)) 
    THEN [Foods].[DisplayName] 
END AS [Food],
CASE 
    WHEN ('AnimalAge' in (select * from @fields)) 
    THEN [Animals].[Age] 
END AS [AnimalAge],
CASE 
    WHEN ('AmountOfFood' in (select * from @fields)) 
    THEN [Animals].[AmountOfFood] 
END AS [AmountOfFood]

我面临的问题是（正如可以预料的那样）我的SP从大约200毫秒到大约需要1秒

有没有办法可以重写这个，以免它杀死我们？

我的王国为一个foreach !!!

Answer 1

我尝试将存储过程转换为Table-Valued函数，并使网格仅从中选择所需的列。

所以你的功能仍然会选择

SELECT
[Animals].[AnimalID] AS [AnimalID],
[Animals].[name] AS [AnimalName],
[Foods].[DisplayName] AS [Food],
[Animals].[Age] AS [AnimalAge],
[Animals].[AmountOfFood] AS [AmountOfFood]

如果客户端仅选择了例如select * AnimalID, Age from myfunction(..)，则只会将这些列传输到客户端。

Answer 2

在SQL Server中，您也可以使用动态SQL执行此操作。类似的东西：

declare @sql nvarchar(max);

select @sql = (select ', '+
                      (case when FieldName = 'Food' then 'Foods.DisplayName'
                            when FieldName = 'AnimalAge' then 'Animals.Age'
                         . . .
                       end)
               from @fields
               for xml path ('')
              );

select @sql = 'select [Animals].[AnimalID] AS [AnimalID], [Animals].[name] AS [AnimalName]'+@sql+RESTOFQUERY;

exec(@sql);

使用CASE时的SQL性能问题

2 个答案: