主题：各科的平均分不能正确统计，请老师看一下问题在哪里

各科的平均分不能正确统计，请老师看一下问题在哪里

Dim b As New SQLGroupTableBuilder("统计表1","学生成绩汇总表")

b.Groups.AddDef("班级")

b.Totals.AddExp("人数","学号","",AggregateEnum.Count) '统计人数

Dim nms() As String = {"语文","数学","英语","物理","政治","历史","地理","生物"}

For Each nm As String In nms '利用表达式统计及格人数和优秀人数 

    b.Totals.AddExp(nm & "_平均",AggregateEnum.Average)

    b.Totals.Addexp(nm & "_及格", "iif(" &  nm & " >= 60, 1, 0)")

    b.Totals.Addexp(nm & "_优秀", "iif(" &  nm & " >= 80, 1, 0)")

    Next

b.VerticalTotal = True

b.Build()

For Each nm As String In nms '对生成的统计表增加表达式列,计算及格率和优秀率

    DataTables("统计表1").DataCols.Add(nm & "_及格率",Gettype(Double), nm & "_及格/人数" )

    Tables("统计表1").Cols(nm & "_及格率").Move(Tables("统计表1").Cols(nm & "_及格").Index + 1)

    DataTables("统计表1").DataCols.Add(nm & "_优秀率",Gettype(Double), nm & "_优秀/人数" )

    Tables("统计表1").Cols(nm & "_优秀率").Move(Tables("统计表1").Cols(nm & "_优秀").Index + 1)

    DataTables("统计表1").DataCols(nm & "_及格率").SetFormat("0.00%")

    DataTables("统计表1").DataCols(nm & "_优秀率").SetFormat("0.00%")

Next

MainTable = Tables("统计表1")