问题: docmd.runsql 语句执行的操作查询如何回滚? 回答: 希望通过Docmd.RUNSQL实现事务的回滚(RollBack)操作
很遗憾的说,Access无法法通过Docmd.RUNSQL来实现事务的回觥4蠹乙残碜⒁獾皆贒ocmd.runsql的语句操作的帮助中,有一个选项是UseTransaction。这个选项的是用来确认是否对该语句进行事务性的操作。假如选择True(默认为True),那么所有的操作都将被当作是一个单独的原子操作来对数据库进行操作;假如选择是False,那么操作将不会被当作事务(在多用户的情况下可能会出现Dirty Read)的情况。但是这些事务都是在内部完成的,我们无法显示的通过申明commit或者rollback来控制其操作。 根据我的经验,ACCESS也无法通过Docmd.OPENQUERY来完成类似的事务显示操作。假如大家希望实现事务的操作,唯一的用法就是通过WorkSpaceObject.BeginTrans来实现。在Access VBA的帮助文件中,大家可以找到如下的示例: 'BeginBeginTransVB 'To integrate this code 'replace the data source and initial catalog values 'in the connection string Public Sub Main() On Error GoTo ErrorHandler 'recordset and connection variables Dim Cnxn As ADODB.Connection Dim strCnxn As String Dim rstTitles As ADODB.Recordset Dim strSQLTitles As String 'record variables Dim strTitle As String Dim strMessage As String ' Open connection strCnxn = "Provider='sqloledb';Data Source='mysqlServer';" & _ "Initial Catalog='Pubs';Integrated Security='SSPI';" Set Cnxn = New ADODB.Connection Cnxn.Open strCnxn ' Open recordset dynamic to allow for changes Set rstTitles = New ADODB.Recordset strSQLTitles = "Titles" rstTitles.Open strSQLTitles, Cnxn, adOpenDynamic, adLockPessimistic, adCmdTable Cnxn.BeginTrans ' Loop through recordset and prompt user ' to change the type for a specified title rstTitles.MoveFirst Do Until rstTitles.EOF If Trim(rstTitles!Type) = "psychology" Then strTitle = rstTitles!Title strMessage = "Title: " & strTitle & vbCr & _ "Change type to self help?" ' If yes, change type for the specified title If MsgBox(strMessage, vbYesNo) = vbYes Then rstTitles!Type = "self_help" rstTitles.Update End If End If rstTitles.MoveNext Loop ' Prompt user to commit all changes made If MsgBox("Save all changes?", vbYesNo) = vbYes Then Cnxn.CommitTrans Else Cnxn.RollbackTrans End If ' Print recordset rstTitles.Requery rstTitles.MoveFirst Do While Not rstTitles.EOF Debug.Print rstTitles!Title & " - " & rstTitles!Type rstTitles.MoveNext Loop ' Restore original data as this is a demo rstTitles.MoveFirst Do Until rstTitles.EOF If Trim(rstTitles!
Type) = "self_help" Then rstTitles!Type = "psychology" rstTitles.Update End If rstTitles.MoveNext Loop ' clean up rstTitles.Close Cnxn.Close Set rstTitles = Nothing Set Cnxn = Nothing Exit Sub ErrorHandler: ' clean up If Not rstTitles Is Nothing Then If rstTitles.State = adStateOpen Then rstTitles.Close End If Set rstTitles = Nothing If Not Cnxn Is Nothing Then If Cnxn.State = adStateOpen Then Cnxn.Close End If Set Cnxn = Nothing If Err <> 0 Then MsgBox Err.Source & "-->" & Err.Description, , "Error" End If End Sub 'EndBeginTransVB 最后,强烈推荐大家阅读下列文档,在文档有一个章节:Transactions在Access中的用法和定义 Advanced Microsoft Jet SQL for Access 2000 http://msdn.microsoft.com/library/default.ASP?url=/library/en-us/dnacc2k/Html/acadvsql.asp
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