这个应该是min函数的问题了,对空值比较有些问题。如下处理一下。
For Each dr As DataRow In DataTables("表A").Select("姓名 is not null")
Dim rlist As new List(of Date)
Dim temp As Date
temp = DataTables("表B").Compute("min(用餐日期)","姓名='" & dr("姓名") & "'")
If temp.year > 1 Then
rlist.Add(temp)
End If
temp = DataTables("表C").Compute("min(报名日期)","姓名='" & dr("姓名") & "'")
If temp.year > 1 Then
rlist.Add(temp)
End If
If rlist.Count > 0 Then
rlist.sort
dr("最早日期")=rlist(0)
Else
dr("最早日期")=Nothing
End If
Next