我会使用 CLR,类似这样的东西(这具有在基于 SET 的操作中工作的优点,而动态 sql 替代方案(即 Abduls 答案)不会):
EDIT:CLR dll (Visual Studio 2008) 的源代码发布在此处:http://www.heavencore.co.uk/filehub/uploaded/EvalFunction.zip
如果您想自己编译程序集,代码如下:
Imports System
Imports System.Data
Imports System.Data.SqlClient
Imports System.Data.SqlTypes
Imports Microsoft.SqlServer.Server
Imports System.Runtime.InteropServices
Partial Public Class UserDefinedFunctions
<Microsoft.SqlServer.Server.SqlFunction()> _
Public Shared Function EVAL(ByVal InputExpression As SqlString) As SqlDecimal
Return Evaluate(InputExpression)
End Function
Private Shared Function Evaluate(ByVal expression As SqlString) As SqlDecimal
Dim expressionStr As String = expression.ToString()
Dim loDataTable = New DataTable()
Dim loDataColumn = New DataColumn("Eval", GetType(Double), expressionStr)
loDataTable.Columns.Add(loDataColumn)
loDataTable.Rows.Add(0)
Return ParseDecimal(loDataTable.Rows(0)("Eval").ToString(), 0)
End Function
Public Shared Function ParseDecimal(ByVal InputStr As String, Optional ByVal ReturnIfFail As Decimal = 0) As Decimal
Dim ParseOutput As Decimal = 0
If Decimal.TryParse(InputStr, ParseOutput) = False Then
Return ReturnIfFail
Else
Return ParseOutput
End If
End Function
End Class
安装并绑定后,您可以执行以下操作:
SELECT Faktor, dbo.Eval(Faktor) as Result FROM Artikel
编辑:好的,我刚刚测试过这个,它在基于集合的操作等中工作正常,安装如下:
-- Enable the CLR to run user-defined functions
EXEC sp_configure
'clr enabled' ,
'1'
GO
RECONFIGURE
GO
-- Set the appropriate database security permission
ALTER DATABASE [TargetDatabase] SET TRUSTWORTHY ON
GO
-- Import the assembly
CREATE ASSEMBLY EvalFunction
FROM 'C:\bin\EvalFunction.dll'
WITH PERMISSION_SET = EXTERNAL_ACCESS;
GO
-- Create the Eval function for easy use
CREATE FUNCTION dbo.Eval
(
@Expression NVARCHAR(255)
)
RETURNS DECIMAL(18, 2)
AS EXTERNAL NAME
EvalFunction.[EvalFunction.UserDefinedFunctions].EVAL
GO