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docmd.runsql语句执行的操作查询如何回滚?
  • 12/31
  • 2008
PLSQL | Oracle 1475 次查看
  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獾皆谀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。如果选择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;如果选择是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。如果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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