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Obtain a FAST_FORWARD Cursor (Native Client OLE DB provider)

  • Άρθρο

Applies to: SQL Server Azure SQL Database Azure SQL Managed Instance Azure Synapse Analytics Analytics Platform System (PDW)

To obtain a forward-only, read-only cursor, set the rowset properties DBPROP_SERVERCURSOR, DBPROP_OTHERINSERT, DBPROP_OTHERUPDATEDELETE, DBPROP_OWNINSERT, and DBPROP_OWNUPDATEDELETE to VARIANT_TRUE.

A complete sample shows how to set the rowset properties to obtain a FAST_FORWARD cursor. After the properties are set, a SELECT statement is executed to retrieve and display the Name column of the Purchasing.Vendor table in the AdventureWorks database.

Important

When possible, use Windows Authentication. If Windows Authentication is not available, prompt users to enter their credentials at run time. Avoid storing credentials in a file. If you must persist credentials, you should encrypt them with the Win32 crypto API.

To obtain FAST_FORWARD cursor

  1. Establish a connection to the data source.

  2. Set the rowset properties DBPROP_SERVERCURSOR, DBPROP_OTHERINSERT, DBPROP_OTHERUPDATEDELETE, DBPROP_OWNINSERT, and DBPROP_OWNUPDATEDELETE to VARIANT_TRUE.

  3. Execute the command.

Example

The following example shows how to set the rowset properties to obtain a FAST_FORWARD cursor. After the properties are set, a SELECT statement is executed to retrieve and display the Name column of the Purchasing.Vendor table in the AdventureWorks database. This sample is not supported on IA64.

The Transact-SQL code samples in this article use the AdventureWorks2022 or AdventureWorksDW2022 sample database, which you can download from the Microsoft SQL Server Samples and Community Projects home page.

Compile with ole32.lib oleaut32.lib and execute the following C++ code listing. This application connects to your computer's default SQL Server instance. On some Windows operating systems, you will need to change (localhost) or (local) to the name of your SQL Server instance. To connect to a named instance, change the connection string from L"(local)" to L"(local)\\name", where name is the named instance. By default, SQL Server Express installs to a named instance. Make sure your INCLUDE environment variable includes the directory that contains 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();  
}