Artículo
03/30/2012

Ejecutar un diagrama de actualización mediante OLE DB (SQLXML 4.0)

En este tema se proporciona un ejemplo funcional del uso de OLE DB para ejecutar un diagrama de actualización.

Usar ICommandStream para establecer un comando XML

La interfaz de OLE DB (versión 2.6 o posterior) ICommandStream pasa un comando como un objeto de secuencia, en lugar de como una cadena.

Esta interfaz permite a un comando estar en cualquier codificación que el analizador XML entienda. Cuando se llama a ICommand::Execute, el texto de comando se lee directamente de la secuencia y no se requiere ninguna conversión. Por tanto, la ejecución de comandos XML mediante la interfaz ICommandStream es más eficaz.

Establecer XML como un comando mediante ICommandStream y recuperar los resultados como un documento XML

La interfaz ICommandStream se puede utilizar para establecer documentos XML como un comando; los resultados se pueden recuperar como un documento XML.

Ejecutar plantillas con consultas XPath

La siguiente plantilla XML compuesta de una consulta XPath se especifica como un comando mediante ICommandStream:

<ROOT xmlns:sql="urn:schemas-microsoft-com:xml-sql">
<sql:xpath-query mapping-schema="Schema.xml">Person.Person</sql:xpath-query>
</ROOT>

La consulta XPath de la plantilla se ejecuta en el siguiente esquema de asignación:

<?xml version="1.0" ?>
<Schema xmlns="urn:schemas-microsoft-com:xml-data" xmlns:dt="urn:schemas-microsoft-com:datatypes" xmlns:sql="urn:schemas-microsoft-com:xml-sql">
<ElementType name="Person.Person" >
<AttributeType name="BusinessEntityID" />
<AttributeType name="FirstName" />
<AttributeType name="LastName" />
<attribute type="BusinessEntityID" />
<attribute type="FirstName" />
<attribute type="LastName" />
</ElementType>
</Schema>

La consulta devuelve todos los elementos de empleado. Con la asignación predeterminada, el elemento <Person.Person> se asigna a la tabla Person.Person en la base de datos AdventureWorks2008R2.

Para establecer XML como un comando y recuperar el resultado como un documento XML

Inicialice y establezca una conexión a la base de datos.
Obtenga la interfaz ICommandStream en ICommand.
Establezca las propiedades de comando necesarias. En este ejemplo, la propiedad SSPROP_STREAM_BASEPATH específica del proveedor está establecida en el directorio donde están almacenados el esquema de asignación y los archivos de plantilla.
Utilice ICommandStream::SetCommandStream para especificar el flujo de comandos. En este ejemplo, la plantilla XML que se ejecuta se lee de un archivo. Esto resulta útil si desea ejecutar plantillas XML grandes.
Ejecute el comando XML mediante ICommand::Execute, solicitando el identificador de interfaz de IID_ISequentialStream.

Procese el resultado. En este ejemplo, el XML que se lee de la secuencia se muestra en la pantalla.

void InitializeAndEstablishConnection();
void SetCommandProperties();
void ProcessResultSet();

#define UNICODE
#define _UNICODE
#define DBINITCONSTANTS
#define INITGUID

#include <stdio.h>
#include <tchar.h>
#include <stddef.h>
#include <windows.h>
#include <iostream.h>
#include <oledb.h>
#include <SQLOLEDB.h>

class CSequentialStream : public ISequentialStream
{
   private:   
      ULONG       m_cRef;              // reference count
      HANDLE      m_hFile;         // handle to the file
      LPWSTR      m_wszFileName;      // the file name

   public:
      CSequentialStream( LPWSTR );
      virtual ~CSequentialStream();

      // IUnknown Methods
      STDMETHODIMP_(ULONG)    AddRef();
      STDMETHODIMP_(ULONG)    Release();
      STDMETHODIMP QueryInterface( REFIID, LPVOID* );

      // ISequentialStream Methods
      STDMETHODIMP Read( 
            /* [out] */ void __RPC_FAR*,
            /* [in]  */ ULONG,
            /* [out] */ ULONG __RPC_FAR* );

      STDMETHODIMP Write( 
            /* [in] */ const void __RPC_FAR*,
            /* [in] */ ULONG,
            /* [out]*/ ULONG __RPC_FAR* );
};

IDBInitialize*       pIDBInitialize     = NULL;
IDBProperties*       pIDBProperties     = NULL;
IDBCreateSession*    pIDBCreateSession  = NULL;
IDBCreateCommand*    pIDBCreateCommand  = NULL;
ICommand*            pICommand          = NULL;
ICommandStream*      pICommandStream    = NULL;
ICommandProperties*    pICommandProperties = NULL;
IColumnsInfo*        pIColumnsInfo      = NULL;
ISequentialStream*    pIXMLOutput      = NULL;
DBCOLUMNINFO*        pDBColumnInfo      = NULL;
IAccessor*           pIAccessor        =  NULL;
DBPROP               InitProperties[4];
DBPROPSET            rgInitPropSet[1];
ULONG                i, j;
HRESULT              hr;
LONG                 cNumRows = 0;
ULONG                lNumCols;
WCHAR*               pStringsBuffer;
DBBINDING*           pBindings;
ULONG                ConsumerBufColOffset = 0;
HACCESSOR            hAccessor;
ULONG                lNumRowsRetrieved;
HROW                 hRows[10];
HROW*                pRows = &hRows[0];
BYTE*                pBuffer;
CSequentialStream    XMLInput( L"Query.xml" );

CSequentialStream::CSequentialStream
(
   LPWSTR      wszFileName
)
:
   m_cRef( 0 ),
   m_hFile( NULL ),
   m_wszFileName( NULL )
{
    // The constructor AddRefs.
    AddRef();

   // Allocate memory for the file name.
   m_wszFileName = (LPWSTR) CoTaskMemAlloc( ( wcslen( wszFileName ) + 1 ) * 2 );

   // Copy the file name.
   wcscpy( m_wszFileName, wszFileName );
}

CSequentialStream::~CSequentialStream
(
)
{
   // Free any allocated memory.
   if( m_wszFileName )
      CoTaskMemFree( m_wszFileName );

   // Close the file.
   if( m_hFile )
      CloseHandle( m_hFile );
}

ULONG    
CSequentialStream::AddRef
(
)
{
    return ++m_cRef;
}



ULONG
CSequentialStream::Release()
{
    if(--m_cRef)
        return m_cRef;

    delete this;
    return 0;
}

HRESULT 
CSequentialStream::QueryInterface
(   
   REFIID riid, 
   void** ppv
)
{
    *ppv = NULL;

    if (riid == IID_IUnknown)
        *ppv = this;

    if (riid == IID_ISequentialStream)
        *ppv = this;

    if(*ppv)
    {
        ((IUnknown*)*ppv)->AddRef();
        return S_OK;
    }

    return E_NOINTERFACE;
}

HRESULT 
CSequentialStream::Read
(
   void *pv, 
   ULONG cb, 
   ULONG* pcbRead
)
{
   ULONG   cBytesRead = 0;

    // Parameter checking.
    if(pcbRead)
        *pcbRead = 0;

    if(!pv)
        return STG_E_INVALIDPOINTER;

    if(cb == 0)
        return S_OK;

   // Do we need to open the file?
   if( m_hFile == NULL )
   {
      // Open the file.
      m_hFile = CreateFile( m_wszFileName, GENERIC_READ, 0, NULL, OPEN_EXISTING, 0, NULL );

      // If the file failed to open, return E_FAIL.
      if( m_hFile == INVALID_HANDLE_VALUE )
         return E_FAIL;
   }

   // Clear the buffer.
   ZeroMemory( pv, cb );

   // Read cb bytes from the stream.
   if( !ReadFile( m_hFile, pv, cb, &cBytesRead, NULL ) )
      return E_FAIL;

   // Inform the user of how many bytes to read.
   if( NULL != pcbRead ) 
      *pcbRead = cBytesRead;

    if(cb != cBytesRead)
        return S_FALSE; 

    return S_OK;
}

HRESULT 
CSequentialStream::Write
(
   const void *pv, 
   ULONG cb, 
   ULONG* pcbWritten
)
{
   // For this example, only a read-only stream is needed.
   return STG_E_CANTSAVE;
}

void main() 
{
   // Call a function to initialize and establish a connection. 
    InitializeAndEstablishConnection();

    // Create a session object.
    if(FAILED(pIDBInitialize->QueryInterface(
                                IID_IDBCreateSession,
                                (void**) &pIDBCreateSession)))
    {
        cout << "Failed to obtain IDBCreateSession interface.\n";
    }

    if(FAILED(pIDBCreateSession->CreateSession(
                                     NULL, 
                                     IID_IDBCreateCommand, 
                                     (IUnknown**) &pIDBCreateCommand)))
    {
        cout << "pIDBCreateSession->CreateSession failed.\n";
    }

    // Access the ICommand interface.
    if(FAILED(pIDBCreateCommand->CreateCommand(
                                    NULL, 
                                    IID_ICommand, 
                                    (IUnknown**) &pICommand)))
    {
        cout << "Failed to access ICommand interface.\n";
    }

   // Get an ICommandStream interface.
   if(FAILED(pICommand->QueryInterface( IID_ICommandStream, (void**) &pICommandStream)))
   {
      cout << "Failed to get an ICommandStream interface.\n";
   }

   // Get an ICommandProperties interface.
   if(FAILED(pICommand->QueryInterface( IID_ICommandProperties, (void**) &pICommandProperties)))
   {
      cout << "Failed to get an ICommandProperties interface.\n";
   }

   // Set the command properties.
   SetCommandProperties();

    // Use SetCommandStream() to specify the command stream.
    if(FAILED(pICommandStream->SetCommandStream(IID_ISequentialStream, DBGUID_DEFAULT, (ISequentialStream*) &XMLInput )))
    {
        cout << "Failed to set command stream.\n";
    }

    // Execute the command.
    if(FAILED(hr = pICommand->Execute(NULL, 
                                    IID_ISequentialStream, 
                                    NULL, 
                                    &cNumRows, 
                                    (IUnknown **) &pIXMLOutput )))
    {
        cout << "Failed to execute command.\n";
    }

    // Process the result set.
    ProcessResultSet(); 

    // Free memory.
   if( pIXMLOutput )
      pIXMLOutput->Release();
   pICommandProperties->Release();
   pICommandStream->Release();
    pICommand->Release();
    pIDBCreateCommand->Release();
    pIDBCreateSession->Release();

    if(FAILED(pIDBInitialize->Uninitialize()))
    {
        /*Uninitialize is not required, but it fails if an interface
        has not been released. This can be used for debugging.
        cout << "Problem uninitializing.\n"; */
    } // endif.
    pIDBInitialize->Release();

    // Release the COM library.
    CoUninitialize();
};

//--------------------------------------------------------------------
void InitializeAndEstablishConnection()
{    
    // Initialize the COM library.
    CoInitialize(NULL);

    // Obtain access to the SQLOLEDB Provider.
    hr = CoCreateInstance(CLSID_SQLOLEDB, 
                          NULL, 
                          CLSCTX_INPROC_SERVER,
                          IID_IDBInitialize, 
                          (void **) &pIDBInitialize);
    if(FAILED(hr))
    {
        printf("Failed to get IDBInitialize interface.\n");
    } // end if

    /*
    Initialize the property values needed 
    to establish the connection.
    */
    for(i = 0; i < 4; i++) 
        VariantInit(&InitProperties[i].vValue);


    // Server name.
    InitProperties[0].dwPropertyID  = DBPROP_INIT_DATASOURCE;
    InitProperties[0].vValue.vt     = VT_BSTR;
    InitProperties[0].vValue.bstrVal= 
                            SysAllocString(L"Server");
    InitProperties[0].dwOptions     = DBPROPOPTIONS_REQUIRED;
    InitProperties[0].colid         = DB_NULLID;

// Database.
    InitProperties[1].dwPropertyID  = DBPROP_INIT_CATALOG;
    InitProperties[1].vValue.vt     = VT_BSTR;
    InitProperties[1].vValue.bstrVal= SysAllocString(L"northwind");
    InitProperties[1].dwOptions     = DBPROPOPTIONS_REQUIRED;
    InitProperties[1].colid         = DB_NULLID;

// Username (login).
    InitProperties[2].dwPropertyID  = DBPROP_AUTH_USERID; 
    InitProperties[2].vValue.vt     = VT_BSTR;
    InitProperties[2].vValue.bstrVal= SysAllocString(L"Login");
    InitProperties[2].dwOptions     = DBPROPOPTIONS_REQUIRED;
    InitProperties[2].colid         = DB_NULLID;

// Password.
//    InitProperties[3].dwPropertyID  = DBPROP_AUTH_PASSWORD; 
//    InitProperties[3].vValue.vt     = VT_BSTR;
//    InitProperties[3].vValue.bstrVal= SysAllocString(L"Password");
//    InitProperties[3].dwOptions     = DBPROPOPTIONS_REQUIRED;
//    InitProperties[3].colid         = DB_NULLID;

    /*
    Now that the properties are set, construct the DBPROPSET structure.
    (rgInitPropSet). The DBPROPSET structure is used to pass an array 
    of DBPROP structures (InitProperties) to the SetProperties method.
    */
    rgInitPropSet[0].guidPropertySet = DBPROPSET_DBINIT;
//  rgInitPropSet[0].cProperties    = 4;
    rgInitPropSet[0].cProperties    = 3;
    rgInitPropSet[0].rgProperties   = InitProperties;

    // Set initialization properties.
    hr = pIDBInitialize->QueryInterface(IID_IDBProperties, 
                                   (void **)&pIDBProperties);
    if(FAILED(hr))
    {
        cout << "Failed to get IDBProperties interface.\n";
    }

    hr = pIDBProperties->SetProperties(1, rgInitPropSet); 
    if(FAILED(hr))
    {
        cout << "Failed to set initialization properties.\n";
    } // end if

    pIDBProperties->Release();

    // Establish the connection to the data source.
    if(FAILED(pIDBInitialize->Initialize()))
    {
        cout << "Problem establishing connection to the data source.\n";
    }
} // End of InitializeAndEstablishConnection.
void SetCommandProperties()
{    
//    for(i = 0; i < 4; i++) 
        VariantInit(&InitProperties[0].vValue);


    // Server name.
    InitProperties[0].dwPropertyID  = SSPROP_STREAM_BASEPATH;
    InitProperties[0].vValue.vt     = VT_BSTR;
    InitProperties[0].vValue.bstrVal= 
                            SysAllocString(L"C:\\MyDir");
    InitProperties[0].dwOptions     = DBPROPOPTIONS_REQUIRED;
    InitProperties[0].colid         = DB_NULLID;


    /*
    Now that the properties are set, construct the DBPROPSET structure
    (rgInitPropSet). The DBPROPSET structure is used to pass an array 
    of DBPROP structures (InitProperties) to the SetProperties method.
    */
    rgInitPropSet[0].guidPropertySet = DBPROPSET_SQLSERVERSTREAM;
    rgInitPropSet[0].cProperties    = 1;
    rgInitPropSet[0].rgProperties   = InitProperties;

    // Set initialization properties.
    hr = pICommandProperties->SetProperties(1, rgInitPropSet); 
    if(FAILED(hr))
    {
        cout << "Failed to set command properties.\n";
    } // end if
} // End of InitializeAndEstablishConnection.

//--------------------------------------------------------------------
// Retrieve and display data resulting from a query.
void ProcessResultSet()
{
   CHAR   szBuf[1000];
   ULONG   ulNumRead;
   HRESULT   hr;

   if( pIXMLOutput == NULL )
      return;

   // Read from the stream.
   ZeroMemory( szBuf, 1000 );
   while( ( hr = pIXMLOutput->Read( szBuf, 1000, &ulNumRead ) ) == S_OK )
   {
      cout << szBuf;
   }
} // Process resultset.

Pasar parámetros a plantillas

En este ejemplo se muestra cómo se pueden pasar los valores de parámetro a comandos XML. Esta plantilla XML se especifica como un comando:

<ROOT xmlns:sql='urn:schemas-microsoft-com:xml-sql'>
<sql:header><sql:param name='Title'>Mr.</sql:param></sql:header>
<sql:query>SELECT TOP 20 * FROM Person.Person
WHERE Title = @Title
FOR XML AUTO</sql:query>
</ROOT>

La plantilla incluye una consulta SQL. La consulta requiere un valor para su parámetro (@Title). Si no se pasa ningún valor de parámetro, se utiliza el valor predeterminado ("Mr.").

Al pasar valores de parámetro a una plantilla, se deben especificar tanto el nombre de parámetro como el valor.

Éste es el código:

#define UNICODE
#define _UNICODE
#define DBINITCONSTANTS
#define INITGUID

#include <stdio.h>
#include <tchar.h>
#include <stddef.h>
#include <windows.h>
#include <iostream.h>
#include "oledb.h"
#include "SQLOLEDB.h"

HRESULT InitializeAndEstablishConnection(IDBInitialize ** ppIDBInitialize);
HRESULT SetCommandProperties(ICommand * pICommand);
HRESULT ProcessResultSet(ISequentialStream * pStreamOutput);

//---------------------------------------------------------------------
// Structure Definition Section
//---------------------------------------------------------------------
struct COLUMNDATA
{
    DBLENGTH    dwLength;   // The length of the data field
    DBSTATUS    dwStatus;   // The status value
    BYTE        bData[1];   // The start of the data field
};

class CSequentialStream : public ISequentialStream
{
    private:    
        ULONG       m_cRef;             // reference count
        HANDLE      m_hFile;            // handle to the file
        LPWSTR      m_wszFileName;      // the file name

    public:
        CSequentialStream( LPWSTR );
        virtual ~CSequentialStream();

        // IUnknown Methods
        STDMETHODIMP_(ULONG)    AddRef();
        STDMETHODIMP_(ULONG)    Release();
        STDMETHODIMP QueryInterface( REFIID, LPVOID* );

        // ISequentialStream Methods
        STDMETHODIMP Read( 
                /* [out] */ void __RPC_FAR*,
                /* [in]  */ ULONG,
                /* [out] */ ULONG __RPC_FAR* );
        
        STDMETHODIMP Write( 
                /* [in] */ const void __RPC_FAR*,
                /* [in] */ ULONG,
                /* [out]*/ ULONG __RPC_FAR* );
};

CSequentialStream::CSequentialStream
(
    LPWSTR      wszFileName
)
:
    m_cRef( 0 ),
    m_hFile( NULL ),
    m_wszFileName( NULL )
{
    // The constructor AddRefs.
    AddRef();

    // Allocate memory for the file name.
    m_wszFileName = (LPWSTR) CoTaskMemAlloc( ( wcslen( wszFileName ) + 1 ) * 2 );

    // Copy the file name
    wcscpy( m_wszFileName, wszFileName );
}

CSequentialStream::~CSequentialStream
(
)
{
    // Free any allocated memory.
    if( m_wszFileName )
        CoTaskMemFree( m_wszFileName );

    // Close the file.
    if( m_hFile )
        CloseHandle( m_hFile );
}

ULONG    
CSequentialStream::AddRef
(
)
{
    return ++m_cRef;
}
ULONG CSequentialStream::Release()
{
    if(--m_cRef)
        return m_cRef;

    delete this;
    return 0;
}

HRESULT CSequentialStream::QueryInterface
(   
    REFIID riid, 
    void** ppv
)
{
    *ppv = NULL;

    if (riid == IID_IUnknown)
        *ppv = this;

    if (riid == IID_ISequentialStream)
        *ppv = this;

    if(*ppv)
    {
        ((IUnknown*)*ppv)->AddRef();
        return S_OK;
    }

    return E_NOINTERFACE;
}

HRESULT CSequentialStream::Read
(
    void *pv, 
    ULONG cb, 
    ULONG* pcbRead
)
{
    ULONG   cBytesRead = 0;

    // Parameter checking.
    if(pcbRead)
        *pcbRead = 0;

    if(!pv)
        return STG_E_INVALIDPOINTER;

    if(cb == 0)
        return S_OK;

    // Do we need to open the file?
    if( m_hFile == NULL )
    {
        // Open the file.
        m_hFile = CreateFile( m_wszFileName, GENERIC_READ, 0, NULL, OPEN_EXISTING, 0, NULL );

        // If we failed to open the file, return E_FAIL.
        if( m_hFile == INVALID_HANDLE_VALUE )
            return E_FAIL;
    }

    // Clear the buffer.
    ZeroMemory( pv, cb );

    // Read cb bytes from the stream.
    if( !ReadFile( m_hFile, pv, cb, &cBytesRead, NULL ) )
        return E_FAIL;

    // Inform the user how many bytes were read.
    if( NULL != pcbRead ) 
        *pcbRead = cBytesRead;

    if(cb != cBytesRead)
        return S_FALSE; 

    return S_OK;
}

HRESULT CSequentialStream::Write
(
    const void *pv, 
    ULONG cb, 
    ULONG* pcbWritten
)
{
    // For purposes of this example, only a read-only stream is needed.
    return STG_E_CANTSAVE;
}
void main() 
{
    HRESULT                 hr = S_OK;
    IDBInitialize         * pIDBInitialize          = NULL;
    IDBCreateSession      * pIDBCreateSession       = NULL;
    IDBCreateCommand      * pIDBCreateCommand       = NULL;
    ICommand              * pICommand               = NULL;
    ICommandStream        * pICommandStream         = NULL;
    ICommandWithParameters* pICommandWithParameters = NULL;
    ICommandText          * pICommandText           = NULL;
    IAccessor             * pIAccessor              = NULL;
    const ULONG             nParams = 1;
    DBPARAMS              * pParams                 = NULL;
    DBPARAMS                params;
    DBBINDING               acDBBinding[nParams];
    DBBINDSTATUS            acDBBindStatus[nParams];
    DBORDINAL               rgParamOrdinals[1];
    DBPARAMBINDINFO         rgParamBindInfo[1];
    const WCHAR           * wszParamName =      L"@CategoryName";
    const WCHAR           * wszDataSourceType = L"DBTYPE_WCHAR";
    BYTE                    sprocparams[1000];
    COLUMNDATA            * pCol = (COLUMNDATA *) sprocparams;
    ISequentialStream     * pStreamOutput       = NULL;
    DBCOLUMNINFO          * pDBColumnInfo       = NULL;
    HACCESSOR               hAccessor;
    CSequentialStream       XMLInput( L"TemplateFile.xml" );

    typedef struct tagSPROCPARAMS
    {
        WCHAR CategoryName[25];
    } SPROCPARAMS;

    CoInitialize(0);

    // Call a function to initialize and establish connection. 
    if (FAILED(hr = InitializeAndEstablishConnection(&pIDBInitialize)))
        goto Cleanup;

    //Create a session object.
    if(FAILED(hr = pIDBInitialize->QueryInterface(
                                IID_IDBCreateSession,
                                (void**) &pIDBCreateSession)))
    {
        cout << "Failed to obtain IDBCreateSession interface.\n";
        goto Cleanup;
    }

    if(FAILED(hr = pIDBCreateSession->CreateSession(
                                     NULL, 
                                     IID_IDBCreateCommand, 
                                     (IUnknown**) &pIDBCreateCommand)))
    {
        cout << "pIDBCreateSession->CreateSession failed.\n";
        goto Cleanup;
    }

    //Access the ICommand interface.
    if(FAILED(hr = pIDBCreateCommand->CreateCommand(
                                    NULL, 
                                    IID_ICommand, 
                                    (IUnknown**) &pICommand)))
    {
        cout << "Failed to access ICommand interface.\n";
        goto Cleanup;
    }
    
    // Get an ICommandStream interface
    if(FAILED(pICommand->QueryInterface( IID_ICommandStream, (void**) &pICommandStream)))
    {
        cout << "Failed to get an ICommandStream interface.\n";
        goto Cleanup;
    }

    //Use SetCommandStream() to specify the command stream.
    if(FAILED(hr = pICommandStream->SetCommandStream(IID_ISequentialStream, DBGUID_DEFAULT, (ISequentialStream*) &XMLInput )))
    {
        cout << "Failed to set command stream.\n";
        goto Cleanup;
    }

    // Set the command properties.
    if (FAILED(hr = SetCommandProperties(pICommand)))
        goto Cleanup;

    //***************************************
    pCol->dwStatus = DBSTATUS_S_OK;
    wcscpy( (LPWSTR) pCol->bData, L"Condiments" );
    pCol->dwLength = wcslen( (LPWSTR) pCol->bData) * sizeof(WCHAR);

    /*Describe the consumer buffer by filling in the array. 
    of DBBINDING structures.  Each binding associates
    a single parameter to the consumer's buffer.*/
    acDBBinding[0].iOrdinal     = 1;
    acDBBinding[0].obLength     = offsetof( COLUMNDATA, dwLength );
    acDBBinding[0].obStatus     = offsetof( COLUMNDATA, dwStatus );
    acDBBinding[0].pTypeInfo    = NULL;
    acDBBinding[0].pObject      = NULL;
    acDBBinding[0].pBindExt     = NULL;
    acDBBinding[0].dwPart       = DBPART_VALUE | DBPART_STATUS | DBPART_LENGTH;
    acDBBinding[0].dwMemOwner   = DBMEMOWNER_CLIENTOWNED;
    acDBBinding[0].dwFlags      = 0;
    acDBBinding[0].bScale       = 0;
    acDBBinding[0].obValue      = offsetof( COLUMNDATA, bData );
    acDBBinding[0].eParamIO     = DBPARAMIO_INPUT;
    acDBBinding[0].cbMaxLen     = 50; 
    acDBBinding[0].wType        = DBTYPE_WSTR;
    acDBBinding[0].bPrecision   = 0;
        
    rgParamOrdinals[0]              = 1;
    rgParamBindInfo[0].bPrecision   = 0;
    rgParamBindInfo[0].bScale       = 0;
    rgParamBindInfo[0].dwFlags      = DBPARAMFLAGS_ISINPUT;
    rgParamBindInfo[0].pwszDataSourceType = (WCHAR *)wszDataSourceType;
    rgParamBindInfo[0].pwszName     = (WCHAR *)wszParamName;
    rgParamBindInfo[0].ulParamSize  = 35;

    if (FAILED(hr = pICommandStream->QueryInterface(
                        IID_ICommandWithParameters,
                        (LPVOID *)&pICommandWithParameters)))
    {
        cout << "Error.\n";
        goto Cleanup;
    }

    if (FAILED(hr = pICommandWithParameters->SetParameterInfo(
                        nParams,
                        rgParamOrdinals,
                        rgParamBindInfo)))
    {
        cout << "Error.\n";
        goto Cleanup;
    }

    //Create an accessor from the above set of bindings.
    if (FAILED(hr = pICommandStream->QueryInterface(
                                    IID_IAccessor, 
                                    (void**)&pIAccessor)))
    {
        cout << "Failed to get IAccessor interface.\n";
        goto Cleanup;
    }

    if (FAILED(hr = pIAccessor->CreateAccessor(
                            DBACCESSOR_PARAMETERDATA,
                            nParams, 
                            acDBBinding, 
                            sizeof(SPROCPARAMS), 
                            &hAccessor,
                            acDBBindStatus)))
    {
        cout << "Failed to create accessor for the defined parameters.\n";
        goto Cleanup;
    }
    /*
    Fill in DBPARAMS structure for the command execution. This structure
    specifies the parameter values in the command and is then passed 
    to Execute.
    */
    params.pData = sprocparams; //pCol->bData; //sprocparams;
    params.cParamSets = 1;
    params.hAccessor = hAccessor;

    pParams = &params;

    //***************************************
    //Execute the command.
    if(FAILED(hr = pICommand->Execute(NULL, 
                                    IID_ISequentialStream, 
                                    pParams, 
                                    NULL, 
                                    (IUnknown **) &pStreamOutput )))
    {
        cout << "Failed to execute command.\n";
        goto Cleanup;
    }

    //Process the result set.
    if (FAILED(hr = ProcessResultSet(pStreamOutput)))
    {
        goto Cleanup;
    }

Cleanup:
    //Free up memory.
    if( pStreamOutput )
        pStreamOutput->Release();
    if (pICommandStream)
        pICommandStream->Release();
    if (pICommand)
        pICommand->Release();
    if (pIDBCreateCommand)
        pIDBCreateCommand->Release();
    if (pIDBCreateSession)
        pIDBCreateSession->Release();
    if (pIDBInitialize)
        pIDBInitialize->Release();

    if (hr)
    {
        IErrorInfo* pErrorInfo = NULL;
        BSTR        bstrDesc = NULL;
        GetErrorInfo(0, &pErrorInfo);
        if (pErrorInfo)
        {
            pErrorInfo->GetDescription(&bstrDesc);
            printf ("\r\nError: %S\r\n", bstrDesc ? bstrDesc : L"Unknown error");
            SysFreeString(bstrDesc);
            pErrorInfo->Release();
        }
    }
    
    //Release the COM library.
    CoUninitialize();
};

//--------------------------------------------------------------------
HRESULT InitializeAndEstablishConnection(IDBInitialize ** ppIDBInitialize)
{
    HRESULT         hr = S_OK;
    IDBInitialize * pIDBInitialize = NULL;
    IDBProperties * pIDBProperties = NULL;
    DBPROP          rgIDBProps[4];
    DBPROPSET       rgIDBPropSet[1];
    int             ii;

    if (!ppIDBInitialize)
        return E_INVALIDARG;

    *ppIDBInitialize = NULL;

    /*
    Initialize the property values needed 
    to establish the connection.
    */
    for(ii = 0; ii < 4; ii++) 
        VariantInit(&rgIDBProps[ii].vValue);

    //Obtain access to the SQLOLEDB provider.
    if(FAILED(hr = CoCreateInstance(CLSID_SQLOLEDB, 
                          NULL, 
                          CLSCTX_INPROC_SERVER,
                          IID_IDBInitialize, 
                          (void **) &pIDBInitialize)))
    {
        printf("Failed to get IDBInitialize interface.\n");
        goto Cleanup;
    }

    //Server name.
    rgIDBProps[0].dwPropertyID  = DBPROP_INIT_DATASOURCE;
    rgIDBProps[0].vValue.vt     = VT_BSTR;
    rgIDBProps[0].vValue.bstrVal= SysAllocString(L"server");
    rgIDBProps[0].dwOptions     = DBPROPOPTIONS_REQUIRED;
    rgIDBProps[0].colid         = DB_NULLID;

//Database.
    rgIDBProps[1].dwPropertyID  = DBPROP_INIT_CATALOG;
    rgIDBProps[1].vValue.vt     = VT_BSTR;
    rgIDBProps[1].vValue.bstrVal= SysAllocString(L"Northwind");
    rgIDBProps[1].dwOptions     = DBPROPOPTIONS_REQUIRED;
    rgIDBProps[1].colid         = DB_NULLID;

//User name (login).
    rgIDBProps[2].dwPropertyID  = DBPROP_AUTH_USERID; 
    rgIDBProps[2].vValue.vt     = VT_BSTR;
    rgIDBProps[2].vValue.bstrVal= SysAllocString(L"sa");
    rgIDBProps[2].dwOptions     = DBPROPOPTIONS_REQUIRED;
    rgIDBProps[2].colid         = DB_NULLID;

//Password.
//    rgIDBProps[3].dwPropertyID  = DBPROP_AUTH_PASSWORD; 
//    rgIDBProps[3].vValue.vt     = VT_BSTR;
//    rgIDBProps[3].vValue.bstrVal= SysAllocString(L"password");
//    rgIDBProps[3].dwOptions     = DBPROPOPTIONS_REQUIRED;
//    rgIDBProps[3].colid         = DB_NULLID;

    /*
    Now that the properties are set, construct the DBPROPSET structure
    (rgInitPropSet). The DBPROPSET structure is used to pass an array 
    of DBPROP structures (rgIDBProps) to the SetProperties method.
    */
    rgIDBPropSet[0].guidPropertySet = DBPROPSET_DBINIT;
//  rgInitPropSet[0].cProperties    = 4;
    rgIDBPropSet[0].cProperties    = 3;
    rgIDBPropSet[0].rgProperties   = rgIDBProps;

    //Set initialization properties.
    if (FAILED(hr = pIDBInitialize->QueryInterface(IID_IDBProperties, 
                                   (void **)&pIDBProperties)))
    {
        cout << "Failed to get IDBProperties interface.\n";
        goto Cleanup;
    }

    if (FAILED(hr = pIDBProperties->SetProperties(1, rgIDBPropSet)))
    {
        cout << "Failed to set initialization properties.\n";
        goto Cleanup;
    } //end if


    //Now establish the connection to the data source.
    if(FAILED(hr = pIDBInitialize->Initialize()))
    {
        cout << "Problem in establishing connection to the data source.\n";
        goto Cleanup;
    }

    *ppIDBInitialize = pIDBInitialize;

Cleanup:
    for(ii = 0; ii < 4; ii++) 
        VariantClear(&rgIDBProps[ii].vValue);

    if (pIDBProperties)
        pIDBProperties->Release();
    return hr;
} //End of InitializeAndEstablishConnection.

HRESULT SetCommandProperties(ICommand * pICommand)
{
    HRESULT     hr = S_OK;
    DBPROP      rgProps[1];
    DBPROPSET   rgPropSet[1];
    ICommandProperties* pICommandProperties = NULL;
   
    VariantInit(&rgProps[0].vValue);
    
    //Server name.
    rgProps[0].dwPropertyID  = SSPROP_STREAM_BASEPATH;
    rgProps[0].vValue.vt     = VT_BSTR;
    rgProps[0].vValue.bstrVal= SysAllocString(L"D:\\Test");
    rgProps[0].dwOptions     = DBPROPOPTIONS_REQUIRED;
    rgProps[0].colid         = DB_NULLID;

    /*
    Now that the properties are set, construct the DBPROPSET structure
    (rgInitPropSet). The DBPROPSET structure is used to pass an array 
    of DBPROP structures (rgProps) to the SetProperties method.
    */
    rgPropSet[0].guidPropertySet = DBPROPSET_SQLSERVERSTREAM;
    rgPropSet[0].cProperties    = 1;
    rgPropSet[0].rgProperties   = rgProps;

    // Get an ICommandProperties interface.
    if(FAILED(pICommand->QueryInterface( IID_ICommandProperties, (void**) &pICommandProperties)))
    {
        cout << "Failed to get an ICommandProperties interface.\n";
        goto Cleanup;
    }

    //Set initialization properties.
    if(FAILED(hr = pICommandProperties->SetProperties(1, rgPropSet)))
    {
        cout << "Failed to set command properties.\n";
        goto Cleanup;
    }
Cleanup:
    VariantClear(&rgProps[0].vValue);
    if (pICommandProperties)
        pICommandProperties->Release();
    return hr;
}

//--------------------------------------------------------------------
//Retrieve and display data resulting from a query.
HRESULT ProcessResultSet(ISequentialStream * pStreamOutput)
{
    CHAR    szBuf[1000];
    ULONG   ulNumRead;
    HRESULT hr;

    if( pStreamOutput == NULL )
        return E_INVALIDARG;

    // Read from the stream
    ZeroMemory( szBuf, 1000 );
    while( ( hr = pStreamOutput->Read( szBuf, 1000, &ulNumRead ) ) == S_OK )
    {
        cout << szBuf;
        cout.flush();
    }
    return hr;
} //ProcessResultSet.

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