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Obtenir un curseur FAST_FORWARD

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Pour obtenir un curseur avant uniquement, en lecture seule, définissez les propriétés d'ensemble de lignes DBPROP_SERVERCURSOR, DBPROP_OTHERINSERT, DBPROP_OTHERUPDATEDELETE, DBPROP_OWNINSERT et DBPROP_OWNUPDATEDELETE sur VARIANT_TRUE.

Un exemple complet montre comment définir les propriétés de l'ensemble de lignes de façon à obtenir un curseur FAST_FORWARD. Une fois les propriétés définies, une instruction SELECT est exécutée pour récupérer et afficher la colonne Name de la table Purchasing.Vendor dans la base de données AdventureWorks.

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Utilisez si possible l'authentification Windows. Si l'authentification Windows n'est pas disponible, invitez les utilisateurs à entrer leurs informations d'identification au moment de l'exécution. Évitez de stocker ces informations dans un fichier. Si vous devez rendre les informations d'identification persistantes, chiffrez-les avec l'API de chiffrement Win32.

Pour obtenir un curseur FAST_FORWARD

  1. Établissez une connexion à la source de données.

  2. Définissez les propriétés d'ensemble de lignes DBPROP_SERVERCURSOR, DBPROP_OTHERINSERT, DBPROP_OTHERUPDATEDELETE, DBPROP_OWNINSERT et DBPROP_OWNUPDATEDELETE sur VARIANT_TRUE.

  3. Exécutez la commande.

Exemple

L'exemple suivant montre comment définir les propriétés de l'ensemble de lignes de façon à obtenir un curseur FAST_FORWARD. Une fois les propriétés définies, une instruction SELECT est exécutée pour récupérer et afficher la colonne Name de la table Purchasing.Vendor dans la base de données AdventureWorks. Cet exemple n'est pas pris en charge sur la plateforme IA64.

Cet exemple requiert l'exemple de base de données AdventureWorks, que vous pouvez télécharger à partir de la page d'accueil des exemples et projets de communautés Microsoft SQL Server.

Compilez avec ole32.lib oleaut32.lib et exécutez le code C++ suivant. Cette application vous permet de vous connecter à l'instance de SQL Server par défaut de votre ordinateur. Sur certains systèmes d'exploitation Windows, vous devrez remplacer (localhost) ou (local) par le nom de votre instance SQL Server. Pour vous connecter à une instance nommée, remplacez la chaîne de connexion L"(local)" par L"(local)\\name", où name correspond à l'instance nommée. Par défaut, SQL Server Express est installé dans une instance nommée. Assurez-vous que votre variable d'environnement INCLUDE inclut le répertoire qui contient sqlncli.h.

// compile with: ole32.lib oleaut32.lib
#define INITGUID
#define DBINITCONSTANTS
#define OLEDBVER 0x0250   // to include correct interfaces

#include <windows.h>
#include <stdio.h>
#include <oledb.h>
#include <sqlncli.h>
#include <oledberr.h>

IDBInitialize* pIDBInitialize = NULL;
ICommandText* pICommandText = NULL;

// Connect to the server and create a command object.
int InitializeAndConnect();

// Set the properties to get a FAST_FORWARD cursor.
int SetRowsetProperties();

// This function executes a command and displays the results.
int ExecuteAndDisplay();

// Release memory.
void Cleanup();

int main() {
   if (InitializeAndConnect() == -1) {
      // Handle error.
      printf("Failed to initialize and connect to the server.\n");
      return -1;
   }

   // Set the row properties to FAST_FORWARD cursor.
   if (SetRowsetProperties() == -1) {
      // Handle error.
      printf("Failed to set the rowset properties.\n");
      return -1;
   }

   // Execute a command and display the results.
   if (ExecuteAndDisplay() == -1) {
      // Handle error.
      printf("Failed to execute a command and display the results.\n");
      return -1;
   }

   Cleanup();
}

int InitializeAndConnect() {
   HRESULT hr = S_OK;

   IDBProperties* pIDBProperties = NULL;
   IDBCreateSession* pIDBCreateSession = NULL;
   IDBCreateCommand* pIDBCreateCommand = NULL;

   DBPROPSET dbPropSet;
   DBPROP dbProp[4];
   int iRetVal = 0;

   // Initialize OLE
   if ( FAILED( hr = OleInitialize( NULL ) ) ) {
      // Handle errors here.
      return -1;
   }

   // Create an instance of Microsoft SQL Server Native Client OLE DB Provider.
   if ( FAILED( hr = 
      CoCreateInstance(CLSID_SQLNCLI11, NULL, CLSCTX_INPROC_SERVER, IID_IDBProperties, (void **) &pIDBProperties ))) {
      // Handle errors here.
      return -1;
   }

   // Set up the connection properties.
   dbProp[0].dwPropertyID = DBPROP_INIT_DATASOURCE;
   dbProp[0].dwOptions = DBPROPOPTIONS_REQUIRED;
   dbProp[0].colid = DB_NULLID;
   V_VT(&(dbProp[0].vValue)) = VT_BSTR;

   V_BSTR(&(dbProp[0].vValue)) = SysAllocString( L"(local)" );

   dbProp[1].dwPropertyID = DBPROP_AUTH_INTEGRATED;
   dbProp[1].dwOptions = DBPROPOPTIONS_REQUIRED;
   dbProp[1].colid = DB_NULLID;
   V_VT(&(dbProp[1].vValue)) = VT_BSTR;
   V_BSTR(&(dbProp[1].vValue)) = SysAllocString( L"SSPI" );

   dbProp[2].dwPropertyID = DBPROP_NULLCOLLATION;
   dbProp[2].dwOptions = DBPROPOPTIONS_REQUIRED;
   dbProp[2].colid = DB_NULLID;
   V_VT(&(dbProp[2].vValue)) = VT_BSTR;
   V_BSTR(&(dbProp[2].vValue)) = SysAllocString( L"" );

   dbProp[3].dwPropertyID = DBPROP_INIT_CATALOG;
   dbProp[3].dwOptions = DBPROPOPTIONS_REQUIRED;
   dbProp[3].colid = DB_NULLID;
   V_VT(&(dbProp[3].vValue)) = VT_BSTR;
   V_BSTR(&(dbProp[3].vValue)) = SysAllocString( L"AdventureWorks" );

   dbPropSet.rgProperties = dbProp;
   dbPropSet.cProperties = 4;
   dbPropSet.guidPropertySet = DBPROPSET_DBINIT;

   if ( FAILED( hr = pIDBProperties->SetProperties( 1, &dbPropSet ))) {
      // Handle errors here.
      iRetVal = -1;
      goto CLEANUP;
   }

   SysFreeString( V_BSTR(&(dbProp[0].vValue)) );
   SysFreeString( V_BSTR(&(dbProp[1].vValue)) );
   SysFreeString( V_BSTR(&(dbProp[2].vValue)) );
   SysFreeString( V_BSTR(&(dbProp[3].vValue)) );

   // Get an IDBInitialize interface.
   if ( FAILED( hr = 
      pIDBProperties->QueryInterface( IID_IDBInitialize, (void **) &pIDBInitialize ))) {
      // Handle errors here.
      iRetVal = -1;
      goto CLEANUP;
   }

   // Call Initialize.
   if ( FAILED( hr = pIDBInitialize->Initialize())) {
      // Handle errors here.
      iRetVal = -1;
      goto CLEANUP;
   }

   // Get a IDBCreateSession interface.
   if ( FAILED( hr = 
      pIDBInitialize->QueryInterface( IID_IDBCreateSession, (void **) &pIDBCreateSession ))) {
      // Handle errors here.
      iRetVal = -1;
      goto CLEANUP;
   }

   // Create a session
   if ( FAILED( hr = 
      pIDBCreateSession->CreateSession( NULL, IID_IDBCreateCommand, (IUnknown **) &pIDBCreateCommand))) {
      // Handle errors here.
      iRetVal = -1;
      goto CLEANUP;
   }

   // Create a command.
   if ( FAILED( hr = 
      pIDBCreateCommand->CreateCommand( NULL, IID_ICommandText, (IUnknown **) &pICommandText))) {
      // Handle errors here.
      iRetVal = -1;
      goto CLEANUP;
   }

CLEANUP:
   // Release all the objects not needed anymore.
   pIDBProperties->Release();
   if ( pIDBCreateSession )
      pIDBCreateSession->Release();
   if ( pIDBCreateCommand )
      pIDBCreateCommand->Release();

   return iRetVal;
}

int SetRowsetProperties() {
   HRESULT hr = S_OK;
   ICommandProperties* pICommandProperties = NULL;
   DBPROPSET dbPropSet;
   DBPROP dbProp[5];
   int iRetVal = 0;

   // Get an ICommandProperties object.
   if ( FAILED( hr = 
      pICommandText->QueryInterface( IID_ICommandProperties, (void **) &pICommandProperties ))) {
      // Handle errors here.
      return -1;
   }

   // Set up the properties to get a FAST_FORWARD cursor.
   dbProp[0].dwPropertyID       = DBPROP_SERVERCURSOR;
   dbProp[0].dwOptions          = DBPROPOPTIONS_REQUIRED;
   dbProp[0].colid              = DB_NULLID;
   V_VT(&(dbProp[0].vValue))    = VT_BOOL;
   V_BOOL(&(dbProp[0].vValue))  = VARIANT_TRUE;

   dbProp[1].dwPropertyID       = DBPROP_OTHERINSERT;
   dbProp[1].dwOptions          = DBPROPOPTIONS_REQUIRED;
   dbProp[1].colid              = DB_NULLID;
   V_VT(&(dbProp[1].vValue))    = VT_BOOL;
   V_BOOL(&(dbProp[1].vValue))  = VARIANT_TRUE;

   dbProp[2].dwPropertyID       = DBPROP_OTHERUPDATEDELETE;
   dbProp[2].dwOptions          = DBPROPOPTIONS_REQUIRED;
   dbProp[2].colid              = DB_NULLID;
   V_VT(&(dbProp[2].vValue))    = VT_BOOL;
   V_BOOL(&(dbProp[2].vValue))  = VARIANT_TRUE;

   dbProp[3].dwPropertyID       = DBPROP_OWNINSERT;
   dbProp[3].dwOptions          = DBPROPOPTIONS_REQUIRED;
   dbProp[3].colid              = DB_NULLID;
   V_VT(&(dbProp[3].vValue))    = VT_BOOL;
   V_BOOL(&(dbProp[3].vValue))  = VARIANT_TRUE;

   dbProp[4].dwPropertyID       = DBPROP_OWNUPDATEDELETE;
   dbProp[4].dwOptions          = DBPROPOPTIONS_REQUIRED;
   dbProp[4].colid              = DB_NULLID;
   V_VT(&(dbProp[4].vValue))    = VT_BOOL;
   V_BOOL(&(dbProp[4].vValue))  = VARIANT_TRUE;

   dbPropSet.rgProperties       = dbProp;
   dbPropSet.cProperties        = 5;
   dbPropSet.guidPropertySet    = DBPROPSET_ROWSET;

   if ( FAILED( hr = pICommandProperties->SetProperties( 1, &dbPropSet))) {
      // Handle errors here.
      iRetVal = -1;
   }

   // Release the ICommandProperties object.
   pICommandProperties->Release();

   return iRetVal;
}

int ExecuteAndDisplay() {
   HRESULT hr = S_OK;
   IRowset* pIRowset = NULL;
   IAccessor* pIAccessor = NULL;

   BYTE* pData = NULL;
   DBCOUNTITEM cRowsObtained = 0;
   ULONG cCount = 0;

   HROW* pRows = new HROW[10];
   HACCESSOR hAccessor = 0;
   DBBINDING Bind[1];
   int iRetVal = 0;

   if (!pRows)
      return -1;

   // Set the command text.
   if ( FAILED( hr = pICommandText->SetCommandText( DBGUID_SQL, L"select Name from Purchasing.Vendor")))
      // Handle errors and free the memory here.
      return -1;

   // Execute the command.
   if ( FAILED( hr = pICommandText->Execute( NULL, IID_IRowset, NULL, NULL, (IUnknown **) &pIRowset )))
      // Handle errors and free the memory here.
      return -1;

    // Set up the binding structure for Name (nvarchar(50)).
    Bind[0].dwPart      = DBPART_VALUE;
    Bind[0].eParamIO    = DBPARAMIO_NOTPARAM;
    Bind[0].iOrdinal    = 1;
    Bind[0].pTypeInfo   = NULL;
    Bind[0].pObject     = NULL;
    Bind[0].pBindExt    = NULL;
    Bind[0].dwFlags     = 0;
    Bind[0].dwMemOwner  = DBMEMOWNER_CLIENTOWNED;
    Bind[0].obLength    = 0;
    Bind[0].obStatus    = 0;
    Bind[0].obValue     = 0;
    Bind[0].cbMaxLen    = 102;
    Bind[0].wType       = DBTYPE_WSTR;
    Bind[0].bPrecision  = 0;
    Bind[0].bScale      = 0;

   // Get an IAccessor interface.
   if ( FAILED( hr = pIRowset->QueryInterface( IID_IAccessor, (void **) &pIAccessor))) {
      // Handle errors and free the memory here.
      iRetVal = -1;
      goto CLEANUP;
   }

   // Create an accessor.
   if ( FAILED( hr = 
      pIAccessor->CreateAccessor(  DBACCESSOR_ROWDATA, 1, Bind, 0, &hAccessor, NULL))) {
      // Handle errors and free the memory here.
      iRetVal = -1;
      goto CLEANUP;
   }

   // Allocate memory for the data.
   pData = new BYTE[102];
   if (!(pData /* = new BYTE[102] */ )) {
      // Handle errors and free the memory here.
      iRetVal = -1;
      goto CLEANUP;
   }

   // Loop through all of the rows.
   for ( ; ; ) {
      if (FAILED( hr = pIRowset->GetNextRows( NULL, 0, 10, &cRowsObtained, &pRows))) {
         // Handle errors and free the memory here.
         iRetVal = -1;
         goto CLEANUP;
      }

      // Make sure some rows were obtained.
      if (cRowsObtained == 0)
         break;

      // Get the data for the each of the rows.
      for ( cCount = 0 ; cCount < cRowsObtained ; cCount++ ) {
         // Get the row data needed.
         if ( FAILED( hr = pIRowset->GetData( pRows[cCount], hAccessor, pData ))) {
            // Handle errors and free the memory here.
            iRetVal = -1;
            goto CLEANUP;
         }

         // Display row data.
         printf( "%S\n", pData);
      }

      // Release the rows.
      if ( FAILED( hr = pIRowset->ReleaseRows(cRowsObtained, pRows, NULL, NULL, NULL ))) {
         // Handle errors and free the memory here.
         iRetVal = -1;
         goto CLEANUP;
      }
   }

CLEANUP:
   // Release memory allocated for the data.
   delete [] pRows;
   delete [] pData;

   // Release the HACCESSOR.
   if (pIAccessor) {
      pIAccessor->ReleaseAccessor( hAccessor, NULL );

      // Release the IAccessor object.
      pIAccessor->Release();
   }

   // Release the rowset.
   pIRowset->Release();

   return iRetVal;
}

void Cleanup() {
   HRESULT hr = S_OK;

   // Release the ICommandText object.
   pICommandText->Release();

   // Uninitialize the IDBInitialize object.
   if ( FAILED( hr = pIDBInitialize->Uninitialize())) {
      // Handle errors here.
   }

   // Release the IDBInitialize object.
   pIDBInitialize->Release();

   // Uninitialize OLE.
   OleUninitialize();
}