主题：sql连接两个表后为什么提示这个错误？（OK）

Dim cmd As New SQLCommand

cmd.C

cmd.CommandText = "SELECT Distinct a.父件编码 From {BOM} a Left Join (Select 产品编码,品名 From {产品编码}) b on a.父件编码=b.产品编码"

Dim dt As DataTable = cmd.ExecuteReader()

If dt.DataRows.Count > 0 Then

    For Each dr As DataRow In dt.datarows

        Dim s As String = dr("品名")

        If s > "" Then

            output.show(dr("品名"))

        End If

    Next

End If