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How to: Mark a Position in a DAO Recordset

Access Developer Reference

A bookmark is a system-generated Byte array that uniquely identifies each record. The DAO Bookmark property of a Recordset object changes each time you move to a new record. To identify a record, move to that record and then assign the value of the DAO Bookmark property to a variable of type Variant. To return to the record, set the DAO Bookmark property to the value of the variable.

The following example illustrates how to find the product that makes the most and least revenue per category by using a bookmark to save the current record position. By using a bookmark, you can perform other operations on the Recordset object, and then return to the saved record position.

  Sub GetProductStats()

Dim dbsNorthwind As DAO.Database Dim rstProducts As DAO.Recordset Dim rstCategories As DAO.Recordset Dim varFirstMark As Variant Dim varHighMark As Variant Dim varLowMark As Variant Dim curHighRev As Currency Dim curLowRev As Currency Dim strSQL As String Dim strCriteria As String Dim strMessage As String

On Error GoTo ErrorHandler

Set dbsNorthwind = CurrentDb

strSQL = "SELECT * FROM Products WHERE UnitsOnOrder >= 40 " & _ "ORDER BY CategoryID, UnitsOnOrder DESC" Set rstProducts = dbsNorthwind.OpenRecordset(strSQL, dbOpenSnapshot) If rstProducts.EOF Then Exit Sub

StrSQL = "SELECT CategoryID, CategoryName FROM Categories " & _ "ORDER BY CategoryID" Set rstCategories = dbsNorthwind.OpenRecordset(strSQL, dbOpenSnapshot)

'For each category find the product generating the least revenue 'and the product generating the most revenue. Do Until rstCategories.EOF

  strCriteria = "CategoryID = " & rstCategories![CategoryID]
  rstProducts.FindFirst strCriteria
  curHighRev = rstProducts![UnitPrice] * rstProducts![UnitsOnOrder]

  If Not rstProducts.NoMatch Then

     'Set bookmarks at the first record containing the CategoryID.
     varFirstMark = rstProducts.Bookmark
     varHighMark = varFirstMark
     varLowMark = varFirstMark

     'Find the product generating the most revenue.
     Do While rstProducts![CategoryID] = rstCategories![CategoryID]
        If rstProducts![UnitPrice] * rstProducts![UnitsOnOrder] > _
        curHighRev Then
           curHighRev = rstProducts![UnitPrice] * _
                        rstProducts![UnitsOnOrder]
           varHighMark = rstProducts.Bookmark
        End If
        rstProducts.MoveNext
     Loop

     'Move to the first record containing the CategoryID.
     rstProducts.Bookmark = varFirstMark
     curLowRev = rstProducts![UnitPrice] * rstProducts![UnitsOnOrder]

     ' Find the product generating the least revenue.
     Do While rstProducts![CategoryID] = rstCategories![CategoryID]
        If rstProducts![UnitPrice] * rstProducts![UnitsOnOrder] < _
        curLowRev Then
           curLowRev = rstProducts![UnitPrice] * _
                       rstProducts![UnitsOnOrder]
           varLowMark = rstProducts.Bookmark
        End If
        rstProducts.MoveNext
     Loop

  End If

  'Set high and low bookmarks to build the message string.
  strMessage = "CATEGORY:  " & rstCategories!CategoryName & _
               vbCrLf & vbCrLf
  rstProducts.Bookmark = varHighMark
  strMessage = strMessage & "HIGH: $" & curHighRev & "  " & _
               rstProducts!ProductName & vbCrLf
  rstProducts.Bookmark = varLowMark
  strMessage = strMessage & "LOW:  $" & curLowRev & "  " & _
               rstProducts!ProductName
  MsgBox strMessage, , "Product Statistics"
  rstCategories.MoveNext

Loop

rstProducts.Close rstCategories.Close dbsNorthwind.Close

Set rstProducts = Nothing Set rstCategories = Nothing Set dbsNorthwind = Nothing

Exit Sub

ErrorHandler: MsgBox "Error #: " & Err.Number & vbCrLf & vbCrLf & Err.Description End Sub

A bookmark is particularly useful if a method fails because the current record position is undefined.

The LastModified property of the Recordset object provides a good illustration of how to use a bookmark. The LastModified property returns the bookmark of the last record in the Recordset to be added or modified. To use it, set the DAO Bookmark property equal to the LastModified property, as follows:

  rstCustomers.Bookmark = rstCustomers.LastModified

This moves the current record position to the last record that was added or modified. This is particularly useful when adding new records, because after you add a new record, the current record is the one you were on before you added the record. With the LastModified property, you can move to the newly added record if that is what your application expects.

When you close a Recordset object, any bookmarks you saved become invalid. You cannot use a bookmark from one Recordset in another Recordset, even if both Recordset objects are based on the same underlying table or query. However, you can use a bookmark on the clone of a Recordset, as shown in the following example:

  Dim dbsNorthwind As DAO.Database
Dim rstOriginal As DAO.Recordset
Dim rstDuplicate As DAO.Recordset
Dim varBookMark As Variant

Set dbsNorthwind = CurrentDb

'Create the first Recordset. Set rstOriginal = dbsNorthwind.OpenRecordset("Orders", dbOpenDynaset)

'Save the current record position. varBookMark = rstOriginal.Bookmark

'Create a duplicate Recordset. Set rstDuplicate = rstOriginal.Clone()

'Go to the same record. rstDuplicate.Bookmark = varBookMark

rstOriginal.Close

You can also use the DAO Bookmark property on the Recordset object underlying a form. With this property, your code can mark which record is currently displayed on the form, and then change the record that is being displayed. For example, on a form containing employee information, you may want to include a button that a user can click to show the record for an employee's supervisor.

Bb243795.vs_note(en-us,office.12).gif  Note
Dynasets based on certain linked tables, such as Paradox tables that have no primary key, do not support bookmarks, nor do forward-only-type Recordset objects. You can determine whether a given Recordset object supports bookmarks by checking the value of the Bookmarkable property.