Méthodes BeginTrans, CommitTrans et RollbackTrans, exemple (VB)
Cet exemple montre comment modifier le type de livre de tous les livres de psychologie dans la table Titles de la base de données. Après que la méthode BeginTrans démarre une transaction qui isole toutes les modifications apportées à la table Titles, la méthode CommitTrans enregistre les modifications. Vous pouvez utiliser la méthode RollbackTrans pour annuler les modifications que vous avez enregistrées à l’aide de la méthode Update.
'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
Voir aussi
BeginTrans, CommitTrans et RollbackTrans, méthodes (ADO)
Connection, objet (ADO)