Пример метода CompareBookmarks (Visual Basic)

В этом примере демонстрируется метод CompareBookmarks . Относительное значение закладок требуется редко, если только конкретная закладка не является какой-то особой.

Назначьте случайную строку набора записей , производного от таблицы Авторы , в качестве целевого объекта поиска. Затем отобразите положение каждой строки относительно этого целевого объекта.

'BeginCompareBookmarksVB  
  
    '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 rstAuthors As ADODB.Recordset  
    Dim Cnxn As ADODB.Connection  
    Dim strSQLAuthors As String  
    Dim strCnxn As String  
  
     ' comparison variables  
    Dim count As Integer  
    Dim target As Variant  
    Dim result As Long  
    Dim strAnswer As String  
    Dim strTitle As String  
    strTitle = "CompareBookmarks Example"  
  
    ' Open a connection  
    Set Cnxn = New ADODB.Connection  
    strCnxn = "Provider='sqloledb';Data Source='MySqlServer';" & _  
        "Initial Catalog='Pubs';Integrated Security='SSPI';"  
    Cnxn.Open strCnxn  
  
     ' Open recordset as a static cursor type recordset  
    Set rstAuthors = New ADODB.Recordset  
    strSQLAuthors = "SELECT * FROM Authors"  
    rstAuthors.Open strSQLAuthors, Cnxn, adOpenStatic, adLockReadOnly, adCmdText  
  
    count = rstAuthors.RecordCount  
    Debug.Print "Rows in the Recordset = "; count  
  
     ' Exit if an empty recordset  
    If count = 0 Then Exit Sub  
  
     ' Get position between 0 and count -1  
    Randomize  
    count = (Int(count * Rnd))  
    Debug.Print "Randomly chosen row position = "; count  
     ' Move row to random position  
    rstAuthors.Move count, adBookmarkFirst  
     ' Remember the mystery row  
    target = rstAuthors.Bookmark  
  
    count = 0  
    rstAuthors.MoveFirst  
         ' Loop through recordset  
    Do Until rstAuthors.EOF  
       result = rstAuthors.CompareBookmarks(rstAuthors.Bookmark, target)  
  
       If result = adCompareNotEqual Then  
          Debug.Print "Row "; count; ": Bookmarks are not equal."  
       ElseIf result = adCompareNotComparable Then  
          Debug.Print "Row "; count; ": Bookmarks are not comparable."  
       Else  
          Select Case result  
             Case adCompareLessThan  
                strAnswer = "less than"  
             Case adCompareEqual  
                strAnswer = "equal to"  
             Case adCompareGreaterThan  
                strAnswer = "greater than"  
             Case Else  
                strAnswer = "in error comparing to"  
          End Select  
            'show the results row-by-row  
          Debug.Print "Row position " & count & " is " & strAnswer & " the target."  
       End If  
  
       count = count + 1  
       rstAuthors.MoveNext  
    Loop  
  
    ' clean up  
    rstAuthors.Close  
    Cnxn.Close  
    Set rstAuthors = Nothing  
    Set Cnxn = Nothing  
    Exit Sub  
  
ErrorHandler:  
    ' clean up  
    If Not rstAuthors Is Nothing Then  
        If rstAuthors.State = adStateOpen Then rstAuthors.Close  
    End If  
    Set rstAuthors = 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  
'EndCompareBookmarksVB  

См. также:

Метод CompareBookmarks (ADO)
CompareEnum
Объект Recordset (ADO)