主题：录入客户资料，禁止编号重复的问题

Dim cmd1 As New SQLCommand

    Dim cmd2 As New SQLCommand

    Dim Key As Integer

    cmd1.C '设置数据源名称

    cmd2.C

    cmd1.commandText = "Select Count(*) F rom [单据编号] Where 单据前缀 = 'KHGL-'"

messagebox.show("1")

    If cmd1.ExecuteScalar = 0 Then '如果编号表不存在前缀的行,那么增加一行

        cmd1.commandtext = "In sert Into 单据编号 (单据前缀,顺序号) Values('KHGL-',1)"

        cmd1.ExecuteNonQuery

    End If

    cmd1.commandText = "Select [顺序号] F rom [单据编号] Where 单据前缀 = 'KHGL-'"

    Key = cmd1.ExecuteScalar() '从后台获得顺序号

    cmd2.co mmandText = "Up date [单据编号] Set [顺序号] = " & (Key + 1) & " Where [顺序号] = " & Key & " And [单据前缀] = 'KHGL-'"  

    If cmd2.ExecuteNonQuery() = 0 Then