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我正在为 SQL Server 2008 编写一些自定义的 .Net 扩展。其中一个是用户定义的聚合，它应该将一组十进制数字聚合为一个十进制值。

为了缩小我的问题，我使用了一个简单的Const聚合，它只返回一个常量十进制值。将此作为用户定义的聚合添加到 SQL Server 时，返回的值总是四舍五入：

SELECT dbo.Const(n, 2.5) from (select 1 n) x -- returns 3, not 2.5

我错过了什么？

这是代码：

using System;
using System.Data.SqlTypes;
using System.IO;
using Microsoft.SqlServer.Server;
using SqlServer.Clr.Extensions.Aggregates.Implementation;

[Serializable]
[SqlUserDefinedAggregate(Format.UserDefined,MaxByteSize = -1)]
public class Const : IBinarySerialize
{
    private decimal _constValue;

    public void Init() {}

    public void Accumulate(SqlDecimal value, SqlDecimal constValue)
    {
        _constValue = constValue.Value;
    }

    public void Merge(Const value) {}

    public SqlDecimal Terminate()
    {
        return new SqlDecimal(_constValue);
    }

    public void Read(BinaryReader r)
    {
        _constValue = r.ReadDecimal();
    }

    public void Write(BinaryWriter w)
    {
        w.Write(_constValue);
    }
}

将此代码编译为名为SqlServer.Clr.Extensions.dll. 以下脚本可用于将其添加到 SQL Server 并验证意外行为：

use [MyDb] -- replace with your db name
go

-- drop the Const aggregate if it exists
IF EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[Const]'))
    DROP AGGREGATE [Const]
GO
-- drop the assembly if it exists
IF  EXISTS (SELECT * FROM sys.assemblies asms WHERE asms.name = N'SqlServer.Clr.Extensions' and is_user_defined = 1)
    DROP ASSEMBLY [SqlServer.Clr.Extensions]
GO

-- import the assembly
CREATE ASSEMBLY [SqlServer.Clr.Extensions]
AUTHORIZATION [dbo]
    FROM 'C:\Path\To\SqlServer.Clr.Extensions.dll'
WITH PERMISSION_SET = SAFE
GO

CREATE AGGREGATE [Const](@input decimal, @constValue decimal)
    RETURNS decimal
    EXTERNAL NAME [SqlServer.Clr.Extensions].[Const] -- put the Const class is in the global namespace
GO

SELECT dbo.Const(n, 2) from (select 1 n) x
SELECT dbo.Const(n, 2.5) from (select 1 n) x
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1 回答 1

1

您必须更改@constvalue decimal为@constvalue decimal(13,2)

Create aggregate [const](@input decimal, @constvalue decimal)
于 2011-02-27T19:07:59.933 回答