你是要这样的结果吗？：：：：：

dim b As New SQLGroupTableBuilder("统计表1","jlj")
b.Groups.AddDef("批次")
b.Totals.AddDef("合格蛋数")
b.Exprs.Adddef("产蛋率","[合格蛋数]/[存栏母鸡]")
b.Exprs.Adddef("入舍鸡产蛋率","[合格蛋数]/[进栏母鸡]")
b.build

with DataTables("统计表1")
    .DataCols.Add("淘汰", GetType(Integer))
End With

For Each r As Row In Tables("统计表1").Rows
    r("淘汰")  = DataTables("jlj").Compute("Sum(淘汰)", "批次 = \'" & r("批次") & "\'")
Next

Tables("窗口1_Table1").DataSource = DataTables("统计表1")
Tables("窗口1_Table1").Cols("淘汰").Move(1)

Maintable = Tables("统计表1")
dim n as integer = CurrentTable.Count
Dim Sum As Integer = DataTables("统计表1").Compute("Sum(产蛋率)")
Dim Sum1 As Integer = DataTables("统计表1").Compute("Sum(入舍鸡产蛋率)")

CurrentTable.AddNew()
currenttable.current("批次") = "平均数"
currenttable.current("产蛋率") = Sum/n
currenttable.current("入舍鸡产蛋率") = Sum1/n

结果：

dim b As New SQLGroupTableBuilder("统计表1","jlj")
b.Groups.AddDef("批次")
b.Totals.AddDef("合格蛋数")
b.build

with DataTables("统计表1")
    .DataCols.Add("淘汰", GetType(Integer))
    .DataCols.Add("产蛋率", GetType(Double))
    .DataCols.Add("入舍鸡产蛋率", GetType(Double))
End With

Tables("统计表1").Cols("淘汰").Move(1)

Maintable = Tables("统计表1")
Tables("窗口1_Table1").DataSource = DataTables("统计表1")
Tables("窗口1_Table1").Cols("淘汰").Move(1)
For i as integer = 0 to Tables("统计表1").count -1
    dim r as row = Tables("统计表1").Rows(i)
    dim n0 as integer = DataTables("jlj").Compute("Count(产蛋率)", "批次 = \'" & r("批次") & "\'")
    dim n as integer = DataTables("jlj").Compute("Count(入舍鸡产蛋率)", "批次 = \'" & r("批次") & "\'")

    Dim Sum As Double = DataTables("jlj").Compute("Sum(产蛋率)", "批次 = \'" & r("批次") & "\'")
    Dim Sum1 As Double = DataTables("jlj").Compute("Sum(入舍鸡产蛋率)", "批次 = \'" & r("批次") & "\'")
   
    r("淘汰")  = DataTables("jlj").Compute("Sum(淘汰)", "批次 = \'" & r("批次") & "\'")
    r("产蛋率")  = Sum/n0
    r("入舍鸡产蛋率")  = Sum1/n   \'这是简单算术平均数，加权平均数公式自己搞定吧。
Next

结果：
此主题相关图片如下：未命名1.jpg



但不知为何？ 第二次执行时，会提示错误，说：不存在产蛋率和入舍产蛋率两列？？？ 郁闷啊～ 
为何？＝》Tables("窗口1_Table1")所在窗口要是关闭后重新打开就不会提示了～ ？