Esempio della proprietà Optimize (VB)
In questo esempio viene illustrata la proprietà Optimize dinamica dell'oggetto Campo. Il campo zip della tabella Autori nel database Pubs non è indicizzato. L'impostazione della proprietà Optimize su True nel campo ZIP autorizza ADO a compilare un indice che migliora le prestazioni del metodo Find.
'BeginOptimizeVB
Public Sub Main()
On Error GoTo ErrorHandler
'To integrate this code
'replace the data source and initial catalog values
'in the connection string.
' Declare the recordset and connection variables.
Dim Cnxn As ADODB.Connection
Dim rstAuthors As ADODB.Recordset
Dim strCnxn As String
Dim strSQLAuthors 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 client-side to enable index creation.
Set rstAuthors = New ADODB.Recordset
rstAuthors.CursorLocation = adUseClient
strSQLAuthors = "SELECT * FROM Authors"
rstAuthors.Open strSQLAuthors, Cnxn, adOpenStatic, adLockReadOnly, adCmdText
' Create the index.
rstAuthors!zip.Properties("Optimize") = True
' Find Akiko Yokomoto
rstAuthors.Find "zip = '94595'"
' Show results.
Debug.Print rstAuthors!au_fname & " " & rstAuthors!au_lname & " " & _
rstAuthors!address & " " & rstAuthors!city & " " & rstAuthors!State
rstAuthors!zip.Properties("Optimize") = False 'Delete the index.
' 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
'EndOptimizeVB