sql server 2008中percentile_cont的替代项

Question

在Oracle中运行良好。。。。。。

oracle查询如下

Select distinct channel_id, position_id,datamonth, 
    percentile_cont(.9) within group (order by TRIM_PRE_ELIG_PAY) 
      over (partition by channel_id, position_id, datamonth) as TRIM_PRE_ELIG_PAY_90th_PERC 
from Tablename

但对于SQL Server，我遇到了一个错误。以下是SQL Server 2008:的查询

Select
   distinct channel_id,
   position_id, datamonth, 
   percentile_cont(.9) within group (order by TRIM_PRE_ELIG_PAY) 
     over (partition by channel_id) as TRIM_PRE_ELIG_PAY_90th_PERC 
from table

错误：无法正确分析Select。输出不能为生成。

我知道它可以在SQL Server 2012中正常工作，但在SQL Server 2008 中需要一种替代方法

有人能帮忙吗。。。。。。。。。。。

Answer 1

SQL Server Engine博客上有一个适用于SQL Server 2005+的解决方法

不幸的是，它很长很复杂：我会把链接留给你，而不是试图根据你的查询进行调整。。。

Answer 2

您可以创建一个CLR聚合函数来实现它。唯一的失败是，您将不得不重新安排您的查询。我使用CLR实现了percentile_cont。请阅读此处，了解如何创建CLR。然后，您可以使用此代码来获得与percentile_cont相同的O/P。它比编写多个语句容易得多。

你肯定可以根据你的使用情况对它进行一些改进/调整。

using System;
using System.Data;
using System.Data.SqlClient;
using System.Data.SqlTypes;
using Microsoft.SqlServer.Server;
using System.Collections.Generic;

[Serializable]
[Microsoft.SqlServer.Server.SqlUserDefinedAggregate(
    Format.UserDefined,
    IsInvariantToDuplicates = false,
    IsInvariantToNulls = false,
    IsInvariantToOrder = false,
    MaxByteSize = 8000)]
public struct Percentile_Cont : IBinarySerialize
{
    //Variables to hold the values;
    private List<decimal> _list;
    private decimal _percentile;
    public void Init()
    {
        _list = new List<decimal>();
        _percentile = new decimal();
    }
    public void Accumulate(SqlDecimal value,SqlDecimal percentile)
    {
        if (!value.IsNull)
        {
            _list.Add(value.Value);
            _percentile = (decimal)percentile;
        }
    }
    ///
    /// Merge the partially computed aggregate with this aggregate.
    /// 
    /// The other partial results to be merged
    public void Merge(Percentile_Cont group)
    {
        this._list.AddRange(group._list.ToArray());
    }
    ///
    /// Called at the end of aggregation, to return the results.
    /// 
    /// The percentile of all inputted values
    public SqlDecimal Terminate()
    {
        if (_list.Count == 0)
            return SqlDecimal.Null;
        _list.Sort();
        if (_percentile < 0 || _percentile >= 1)
            return SqlDecimal.Null;
        var index = 
            (int) Math.Ceiling
            (_percentile * _list.Count  + 0.5m);
        if(index > _list.Count)
        {
            index = index - 1;
        }
        return _list[index-1];
    }

    #region IBinarySerialize Members
    public void Read(System.IO.BinaryReader binaryReader)
    {
        int cnt = binaryReader.ReadInt32();
        this._list = new List<decimal>(cnt);
        this._percentile = new decimal();
        for (int i = 0; i < cnt; i++)
        {
            this._list.Add(binaryReader.ReadDecimal());
        }
        this._percentile = binaryReader.ReadDecimal();
    }
    public void Write(System.IO.BinaryWriter binaryWriter)
    {
        binaryWriter.Write(this._list.Count);
        foreach (decimal d in this._list)
        {
            binaryWriter.Write(d);
        }
        binaryWriter.Write(_percentile);
    }
    #endregion
}