在 SQLServer 2005 函数中执行动态 SQL [英] Executing dynamic SQL in a SQLServer 2005 function

问题描述

我先说这个问题，我不认为它是可以解决的.我还有一个解决方法，我可以创建一个带有 OUTPUT 的存储过程来完成此操作，使用函数对需要此校验和的部分进行编码会更容易.

I will preface this question by saying, I do not think it is solvable. I also have a workaround, I can create a stored procedure with an OUTPUT to accomplish this, it is just easier to code the sections where I need this checksum using a function.

由于 Exec SP_ExecuteSQL @SQL 调用，此代码将不起作用.任何人都知道如何在函数中执行动态 SQL?(再一次，我认为这是不可能的.如果是，我很想知道如何解决它！)

This code will not work because of the Exec SP_ExecuteSQL @SQL calls. Anyone know how to execute dynamic SQL in a function? (and once again, I do not think it is possible. If it is though, I'd love to know how to get around it!)

Create Function Get_Checksum
(
    @DatabaseName      varchar(100),
    @TableName         varchar(100)
)
RETURNS FLOAT
AS
BEGIN

 Declare @SQL        nvarchar(4000)
 Declare @ColumnName varchar(100)
 Declare @i          int
 Declare @Checksum   float
 Declare @intColumns table (idRecord int identity(1,1), ColumnName varchar(255))
 Declare @CS         table (MyCheckSum bigint)

 Set @SQL = 
        'Insert Into @IntColumns(ColumnName)' + Char(13) + 
        'Select Column_Name' + Char(13) +
        'From   ' + @DatabaseName + '.Information_Schema.Columns (NOLOCK)' + Char(13) +
        'Where  Table_Name = ''' + @TableName + '''' + Char(13) +
        '       and Data_Type = ''int''' 

 -- print @SQL

 exec sp_executeSql @SQL

 Set @SQL = 
        'Insert Into @CS(MyChecksum)' + Char(13) + 
        'Select '

 Set @i = 1

 While Exists(
       Select 1
       From   @IntColumns
       Where  IdRecord = @i)
 begin
       Select @ColumnName = ColumnName
       From   @IntColumns
       Where  IdRecord = @i

       Set @SQL = @SQL + Char(13) + 
            CASE WHEN @i = 1 THEN 
                 '    Sum(Cast(IsNull(' + @ColumnName + ',0) as bigint))'
                 ELSE
                 '    + Sum(Cast(IsNull(' + @ColumnName + ',0) as bigint))'
            END

       Set @i = @i + 1
 end

 Set @SQL = @SQL + Char(13) + 
      'From ' + @DatabaseName + '..' + @TableName + ' (NOLOCK)'

 -- print @SQL

 exec sp_executeSql @SQL

 Set @Checksum = (Select Top 1 MyChecksum From @CS)

 Return isnull(@Checksum,0)

END
GO

推荐答案

它通常"无法完成，因为 SQL Server 将函数视为确定性的，这意味着对于给定的一组输入，它应该始终返回相同的输出.存储过程或动态 sql 可能是不确定的，因为它可以更改依赖的外部状态，例如表.

It "ordinarily" can't be done as SQL Server treats functions as deterministic, which means that for a given set of inputs, it should always return the same outputs. A stored procedure or dynamic sql can be non-deterministic because it can change external state, such as a table, which is relied on.

鉴于 SQL 服务器中的函数始终是确定性的，从未来的维护角度来看，试图规避这一点是个坏主意，因为这可能会给将来必须支持代码的任何人造成相当大的混乱.

Given that in SQL server functions are always deterministic, it would be a bad idea from a future maintenance perspective to attempt to circumvent this as it could cause fairly major confusion for anyone who has to support the code in future.

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