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Mark a Position in a DAO Recordset

office 365 dev account|Last Updated: 6/12/2017
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1 Contributor

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 code example shows 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 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.

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.

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