Access两表单传参时如何避免重复传递数值（含Args用法）

以下是几种实用的解决思路，从前端校验到底层约束覆盖不同场景：

1. 打开表单前提前校验 #

在点击按钮打开intransfert表单前，先查询目标数据是否已存在，避免无效打开：

Private Sub Command78_Click()
    Dim targetId As Variant
    targetId = Me!Text83.Value
    
    ' 检查transfertdetailquery中是否已有该ID的记录
    Dim checkRs As Recordset
    Set checkRs = CurrentDb.OpenRecordset( _
        "SELECT trnrin FROM transfertdetailquery WHERE trnrin = " & targetId _
    )
    
    If Not checkRs.EOF Then
        MsgBox "该ID已关联过记录，无需重复添加！", vbExclamation
        checkRs.Close
        Set checkRs = Nothing
        Exit Sub
    End If
    
    checkRs.Close
    Set checkRs = Nothing
    
    ' 无重复则正常打开表单
    DoCmd.OpenForm "intransfert", , , , acFormAdd, acDialog, targetId
End Sub

2. 在目标表单加载时校验 #

如果需要在目标表单侧做校验，修改intransfert的Form_Load事件，提前拦截重复值：

Private Sub Form_Load()
    On Error GoTo ErrHandler
    
    If Me.NewRecord Then
        Dim incomingId As Variant
        incomingId = Me.OpenArgs
        
        ' 查询是否已存在重复记录
        Dim checkRs As Recordset
        Set checkRs = CurrentDb.OpenRecordset( _
            "SELECT trnrin FROM transfertdetailquery WHERE trnrin = " & incomingId _
        )
        
        If Not checkRs.EOF Then
            MsgBox "该ID已存在关联记录，无法重复添加！", vbExclamation
            DoCmd.Close acForm, Me.Name
            checkRs.Close
            Set checkRs = Nothing
            Exit Sub
        End If
        
        checkRs.Close
        Set checkRs = Nothing
        
        Me!trnrin = incomingId
    End If
    
ExitSub:
    Exit Sub
ErrHandler:
    MsgBox "加载出错：" & Err.Description, vbCritical
    Resume ExitSub
End Sub

3. 底层数据加唯一约束（最彻底） #

直接在transfertdetailquery对应的基础表上给trnrin字段设置唯一索引，从数据库层面阻止重复值，同时在表单中捕获错误：

1. 打开transfertdetailquery对应的基础表（比如TransferDetails）
2. 进入设计视图，选中trnrin字段，将索引属性设置为「有(无重复)」
3. 在intransfert表单中添加BeforeUpdate事件处理重复错误：

Private Sub Form_BeforeUpdate(Cancel As Integer)
    On Error GoTo DuplicateErr
    
    Exit Sub
    
DuplicateErr:
    ' 3022是Access唯一约束冲突的错误编号
    If Err.Number = 3022 Then
        MsgBox "该ID已存在，无法重复保存！", vbExclamation
        Cancel = True ' 取消当前保存操作
    Else
        MsgBox "保存出错：" & Err.Description, vbCritical
    End If
End Sub

内容的提问来源于stack exchange，提问作者fredi