Artigo
09/28/2010

Executando um diagrama de atualização usando OLE DB (SQLXML 4.0)

Este tópico fornece um exemplo do uso de OLE DB para executar um diagrama de atualização.

Usando ICommandStream para definir um comando XML

A interface OLE DB (versão 2.6 ou posterior) ICommandStream passa um comando como um objeto de fluxo, em vez de como uma cadeia de caracteres.

Essa interface permite que um comando esteja em qualquer codificação compatível com o analisador XML. Quando ICommand::Execute é chamado, o texto de comando é lido diretamente do fluxo e nenhuma conversão é necessária. Portanto, executar comandos XML usando a interface ICommandStream é mais eficiente.

Definindo XML como um comando usando ICommandStream e recuperando os resultados como um documento XML

A interface ICommandStream pode ser usada para definir documentos XML como um comando e os resultados podem ser recuperados como um documento XML.

Executando modelos com consultas XPath

O seguinte modelo XML, que consiste em uma consulta Xpath, é especificado como um comando usando ICommandStream:

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

A consulta XPath no modelo é executada no seguinte esquema de mapeamento:

<?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.Contact" >
<AttributeType name="ContactID" />
<AttributeType name="FirstName" />
<AttributeType name="LastName" />
<attribute type="ContactID" />
<attribute type="FirstName" />
<attribute type="LastName" />
</ElementType>
</Schema>

A consulta retorna todos os elementos do funcionário. Com o mapeamento padrão, o elemento <Person.Contact> mapeia para a tabela Person.Contact no banco de dados AdventureWorks.

Para definir XML como um comando e recuperar resultados como um documento XML

Inicialize e estabeleça uma conexão com o banco de dados.
Obtenha a interface ICommandStream em ICommand.
Defina as propriedades de comando necessárias. Neste exemplo, a propriedade SSPROP_STREAM_BASEPATH específica de provedor é definida como o diretório onde são armazenados o esquema de mapeamento e os arquivos de modelo.
Use ICommandStream::SetCommandStream para especificar o fluxo de comando. Neste exemplo, o modelo XML que está sendo executado é lido de um arquivo. Isso é útil quando você deseja executar modelos XML grandes.
Execute o comando XML com ICommand::Execute, solicitando o ID de interface IID_ISequentialStream.

Processe o resultado. Neste exemplo, o XML lido do fluxo é exibido na tela.

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.

Passando parâmetros para modelos

Este exemplo mostra como valores de parâmetros podem ser passados para comandos XML. Este modelo XML é especificado como um 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.Contact
WHERE Title = @Title
FOR XML AUTO</sql:query>
</ROOT>

O modelo inclui uma consulta SQL. A consulta requer um valor para seu parâmetro (@Title). Se nenhum valor de parâmetro for passado, o valor padrão ("Mr.") será usado.

Ao passar valores de parâmetros para um modelo, o nome e o valor do parâmetro devem ser especificados.

Este é o 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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