Mysql：按月计算每个员工的运行平均值

Question

我有这个表，其中包含员工的姓名和他们在mysql中的电话持续时间。该表如下所示：

Caller	Emplid	Calldate Call_Duration	
Jack	333	1/1/2016	43	
Jack	333	1/2/2016	45	
Jack	333	1/3/2016	87	
Jack	333	2/4/2016	44	
Jack	333	2/5/2016	234	
jack	333	2/6/2016	431	
Jeff 	111	1/1/2016	23	
Jeff 	111	1/2/2016	54	
Jeff 	111	1/3/2016	67	48

我正在尝试按月计算每个员工total_Duration的每日平均运行时间。假设我有4月的每日运行平均值，那么5月的运行平均值应该从5月1日开始到当月31日结束。我尝试过很多方法，mysql没有像sql server那样的pivot和分区功能。每天拨打电话的员工总数都会发生变化，我需要能够动态照顾不会打电话的员工。

  

输出应如下所示：

Caller	Emplid	Calldate Call_Duration	Running_avg
Jack	333	1/1/2016	43	43
Jack	333	1/2/2016	45	44
Jack	333	1/3/2016	87	58.33333333
Jack	333	2/4/2016	44	44
Jack	333	2/5/2016	234	139
Jack	333	2/6/2016	431	236.3333333
Jeff 	111	1/1/2016	23	23
Jeff 	111	1/2/2016	54	38.5
Jeff 	111	1/3/2016	67	48

这是我在下面开始的查询：

SELECT row_number,Month_Year,Callername,Calldate,Caller_Emplid,`Sum of Call`,`Sum of Call`/row_number as AvgCall,
  @`sum of call`:=@`sum of call`+ `sum of call` overallCall,
  @row_number:=row_number overallrow_number,
  @RunningTotal:=@`sum of call`/@row_number runningTotal
FROM 
(SELECT
@row_number:=
CASE WHEN @CallerName=CallerName and date_format(calldate,'%d') = date_format(calldate,'%d') and 
date_format(calldate,'%m') = date_format(calldate,'%m')
THEN @row_number+1                                      
 ELSE 1 END AS row_number,@CallerName:=CallerName AS Callername,Calldate,Caller_Emplid,Month_Year,`Sum of Call`
FROM transform_data_2, (SELECT @row_number:=0,@CallerName:='') AS t
ORDER BY callername) a
  JOIN (SELECT @`Sum of call`:= 0) t