按月累计值的总和

Question

我在SQL Server中进行查询并收到错误

  

＆＃39; order＆＃39;

附近的语法不正确

我已经看过几个关于它的问题，并对代码进行了修改，但我看不出我的错误。

这是查询：

SELECT  
    datepart(month, nota.DT_Sale_Forma_Bill_Exit) AS mon_text,
    sum(SUM(nota.NM_Material)) OVER (ORDER BY datepart(month,nota.DT_Sale_Forma_Bill_Exit)) 
FROM
    DW_DTS_Representative usuario
INNER JOIN 
    DIS_DTS_Invoice_Fact nota ON usuario.SK_Representative =  nota.SK_Representative
INNER JOIN
    DW_DTS_Operation_Nature cfop ON cfop.SK_Operation_Nature = nota.SK_Operation_Nature
INNER JOIN
    DW_DTS_Emitter cli ON cli.SK_Emitter = nota.SK_Emitter
WHERE
    nota.CD_Currency = '1'
    AND nota.CD_Site = '001'
    AND nota.DT_Sale_Forma_Bill_Exit = '2017'
    AND cli.CD_Customer_Group != '16'
GROUP BY 
    datepart(month, nota.DT_Sale_Forma_Bill_Exit)
ORDER BY 
    datepart(month, nota.DT_Sale_Forma_Bill_Exit)