主题：关联表问题搞了三天.都没搞明白,有请老师指点迷津...

Dim cmd As New SQLCommand
Dim ls As DataTable
Dim dt As integer
Dim dr As string = e.form.controls("ComboBox1").Value
cmd.commandtext = "select 第三列 From {表B} where 第一列 = '"& dr &"' and 第二列 is null"
ls = cmd.ExecuteReader()
dt = ls.datarows.count

if dt > 0 Then
Return
Else
  Tables("表A.表B").AddNew()
end if