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Присваивание больших данных

Применимо: SQL Server База данных SQL Azure Управляемый экземпляр SQL Azure azure Synapse Analytics Analytics Platform System (PDW)

Скачать драйвер OLE DB

OLE DB Driver for SQL Server позволяет передавать данные BLOB по указателю на объект хранилища потребителя.

Потребитель создает объект хранилища, содержащий эти данные, и передает поставщику указатель на этот объект. Поставщик считывает данные из объекта в хранилище поставщика и записывает их в столбец BLOB.

Чтобы передать указатель на собственный объект хранилища, потребитель создает метод доступа, связывающий значение со столбцом BLOB. Затем потребитель вызывает метод IRowsetChange::SetData или IRowsetChange::InsertRow с методом доступа, привязывающим столбец BLOB. Он передает указатель на интерфейс хранилища в объекте хранилища потребителя.

В этом подразделе описывается функциональность, обеспечиваемая следующими функциями.

  • IRowset:SetData

  • ICommand::Execute

  • IRowsetUpdate::Update

Как сохранить большой объем данных

Для передачи указателя на свой собственный объект хранения потребитель создает метод доступа, который привязывает значение столбца BLOB, а затем вызывает метод IRowsetChange::SetData или IRowsetChange::InsertRow . Сохранение данных BLOB происходит следующим образом.

  1. Создайте структуру DBOBJECT, описывающую, каким образом должен производиться доступ к столбцу BLOB. Установите для элемента dwFlag структуры DBOBJECT значение STGM_READ, а для элемента iid значение IID_ISequentialStream (используемого интерфейса).

  2. Установите свойства в группе свойств DBPROPSET_ROWSET, чтобы включить возможность обновления для набора строк.

  3. Создайте набор привязок (по одной для каждого столбца) с помощью массива структур DBBINDING. Установите для элемента wType структуры DBBINDING значение DBTYPE_IUNKNOWN, а для элемента pObject — значение указателя на созданную структуру DBOBJECT.

  4. Создайте метод доступа на основе сведений о привязках в массиве структур DBBINDINGS.

  5. Вызовите функцию GetNextRows для выборки следующих строк из набора строк. Вызовите функцию GetData для чтения данных набора строк.

  6. Создайте объект хранилища, содержащий данные (с признаком длины) и вызовите метод IRowsetChange::SetData (или IRowsetChange::InsertRow) с методом доступа, привязывающим столбец BLOB для задания данных.

Пример

Следующий пример показывает получение данных BLOB. В примере создается таблица, добавляется образец записи, эта запись выбирается из набора строк, а затем устанавливается значение поля BLOB.

#define UNICODE  
#define DBINITCONSTANTS  
#define INITGID  
  
#include <windows.h>  
#include <stdio.h>  
#include <stddef.h>  
#include <iostream.h>  
  
#include <oledb.h>  
#include <oledberr.h>  
  
#include <msoledbsql.h>  
  
#define SAFE_RELEASE(pIUnknown) if(pIUnknown) (pIUnknown)->Release();  
HRESULT GetCommandObject(REFIID riid, IUnknown** ppIUnknown);  
HRESULT CreateTable(ICommandText* pICommandText);  
  
class CSeqStream : public ISequentialStream  
{  
public:  
    //Constructors  
    CSeqStream();  
    virtual ~CSeqStream();  
  
    virtual BOOL Seek(ULONG iPos);  
    virtual BOOL Clear();  
    virtual BOOL CompareData(void* pBuffer);  
    virtual ULONG Length()  { return m_cBufSize; };  
  
    virtual operator void* const() { return m_pBuffer; };  
  
    STDMETHODIMP_(ULONG)    AddRef(void);  
    STDMETHODIMP_(ULONG)    Release(void);  
    STDMETHODIMP QueryInterface(REFIID riid, LPVOID *ppv);  
  
    STDMETHODIMP Read(   
            /* [out] */ void __RPC_FAR *pv,  
            /* [in]  */ ULONG cb,  
            /* [out] */ ULONG __RPC_FAR *pcbRead);  
  
    STDMETHODIMP Write(   
            /* [in] */ const void __RPC_FAR *pv,  
            /* [in] */ ULONG cb,  
            /* [out]*/ ULONG __RPC_FAR *pcbWritten);  
  
protected:  
    //Data  
  
private:  
  
    ULONG       m_cRef;         // reference count  
    void*       m_pBuffer;      // buffer  
    ULONG       m_cBufSize;     // buffer size  
    ULONG       m_iPos;         // current index position in the buffer  
};  
  
//class implementation  
  
CSeqStream::CSeqStream()  
{  
    m_iPos         = 0;  
    m_cRef         = 0;  
    m_pBuffer      = NULL;  
    m_cBufSize     = 0;  
  
    //The constructor AddRef's  
    AddRef();  
}  
  
CSeqStream::~CSeqStream()  
{  
    //Shouldn't have any references left  
//    ASSERT(m_cRef == 0);  
    CoTaskMemFree(m_pBuffer);  
}  
  
ULONG    CSeqStream::AddRef(void)  
{  
    return ++m_cRef;  
}  
  
ULONG    CSeqStream::Release(void)  
{  
//    ASSERT(m_cRef);  
  
    if(--m_cRef)  
        return m_cRef;  
  
    delete this;  
    return 0;  
}  
  
HRESULT CSeqStream::QueryInterface(REFIID riid, void** ppv)  
{  
//    ASSERT(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;  
}  
  
BOOL CSeqStream::Seek(ULONG iPos)  
{  
    // Make sure the desired position is within the buffer.  
//    ASSERT(iPos == 0 || iPos < m_cBufSize);  
  
    // Reset the current buffer position.  
    m_iPos = iPos;  
    return TRUE;  
}  
  
BOOL CSeqStream::Clear()  
{  
    //Frees the buffer  
    m_iPos         = 0;  
    m_cBufSize     = 0;  
  
    CoTaskMemFree(m_pBuffer);  
    m_pBuffer = NULL;  
  
    return TRUE;  
}  
  
BOOL CSeqStream::CompareData(void* pBuffer)  
{  
//    ASSERT(pBuffer);  
  
    // Quick and easy way to compare user buffer with the stream.  
    return memcmp(pBuffer, m_pBuffer, m_cBufSize)==0;  
}  
  
HRESULT CSeqStream::Read(void *pv, ULONG cb, ULONG* pcbRead)  
{  
    //Parameter checking  
    if(pcbRead)  
        *pcbRead = 0;  
  
    if(!pv)  
        return STG_E_INVALIDPOINTER;  
  
    if(cb == 0)  
        return S_OK;  
  
    // Actual code.  
    ULONG cBytesLeft = m_cBufSize - m_iPos;  
    ULONG cBytesRead = cb > cBytesLeft ? cBytesLeft : cb;  
  
    // If no more bytes to retrieve return.  
    if(cBytesLeft == 0)  
        return S_FALSE;   
  
    // Copy to users buffer the number of bytes requested or remaining.  
    memcpy_s(pv, sizeof(pv), (void*)((BYTE*)m_pBuffer + m_iPos), cBytesRead);  
    m_iPos += cBytesRead;  
  
    if(pcbRead)  
        *pcbRead = cBytesRead;  
  
    if(cb != cBytesRead)  
        return S_FALSE;   
  
    return S_OK;  
}  
  
HRESULT CSeqStream::Write(const void *pv, ULONG cb, ULONG* pcbWritten)  
{  
    // Parameter checking.  
    if(!pv)  
        return STG_E_INVALIDPOINTER;  
  
    if(pcbWritten)  
        *pcbWritten = 0;  
  
    if(cb == 0)  
        return S_OK;  
  
    // Enlarge the current buffer.  
    m_cBufSize += cb;  
  
    // Need to append to the end of the stream.  
    m_pBuffer = CoTaskMemRealloc(m_pBuffer, m_cBufSize);  
    memcpy_s((void*)((BYTE*)m_pBuffer + m_iPos), sizeof((void*)((BYTE*)m_pBuffer + m_iPos)), pv, cb);  
    // m_iPos += cb;  
  
    if(pcbWritten)  
        *pcbWritten = cb;  
  
    return S_OK;  
}  
//...........................................................  
void main()  
{  
    CoInitialize(NULL);  
  
    DBOBJECT ObjectStruct;  
    ObjectStruct.dwFlags = STGM_READ;  
    ObjectStruct.iid     = IID_ISequentialStream;  
  
    struct BLOBDATA  
    {  
        DBSTATUS            dwStatus;     
        DWORD               dwLength;   
        ISequentialStream*  pISeqStream;  
    };  
  
    BLOBDATA BLOBGetData;  
    BLOBDATA BLOBSetData;  
  
    const ULONG cBindings = 1;  
    DBBINDING rgBindings[cBindings];   
    HRESULT hr = S_OK;  
    IAccessor*          pIAccessor          = NULL;  
    ICommandText*       pICommandText       = NULL;  
    ICommandProperties* pICommandProperties = NULL;  
    IRowsetChange*      pIRowsetChange      = NULL;  
    IRowset*            pIRowset            = NULL;  
    CSeqStream*         pMySeqStream        = NULL;  
    ULONG cRowsObtained = 0;  
    HACCESSOR hAccessor = DB_NULL_HACCESSOR;  
    DBBINDSTATUS rgBindStatus[cBindings];  
    HROW* rghRows = NULL;  
    const ULONG cPropSets = 1;  
    DBPROPSET   rgPropSets[cPropSets];  
    const ULONG cProperties = 1;  
    DBPROP      rgProperties[cProperties];  
    const ULONG cBytes = 10;  
    BYTE        pBuffer[cBytes];  
    ULONG       cBytesRead = 0;  
  
    BYTE pReadData[cBytes];  //read BLOB data in this array  
    memset(pReadData, 0xAA, cBytes);  
  
    BYTE pWriteData[cBytes];  //write BLOB data from this array  
    memset(pWriteData, 'D', cBytes);  
  
    // Get the Command object.  
    hr = GetCommandObject(IID_ICommandText,   
                          (IUnknown**)&pICommandText);  
    if (FAILED(hr))  
    {  
        cout << "Failed to get ICommandText interface.\n";  
        // Release any references and return.  
        goto Exit;  
    } //end if  
  
    // Create table with image column and index.  
    hr = CreateTable(pICommandText);  
    if (FAILED(hr))  
    {  
        cout << "Failed to create table.\n";  
        // Release any references and return.  
        goto Exit;  
    } //end if  
  
    /*  
    Set the DBPROPSET structure.  It is used to pass an array   
    of DBPROP structures to SetProperties().  
    */  
    rgPropSets[0].guidPropertySet = DBPROPSET_ROWSET;  
    rgPropSets[0].cProperties = cProperties;  
    rgPropSets[0].rgProperties = rgProperties;  
  
    // Now set properties in the property group (DBPROPSET_ROWSET).  
    rgPropSets[0].rgProperties[0].dwPropertyID = DBPROP_UPDATABILITY;  
    rgPropSets[0].rgProperties[0].dwOptions = DBPROPOPTIONS_REQUIRED;  
    rgPropSets[0].rgProperties[0].dwStatus = DBPROPSTATUS_OK;  
    rgPropSets[0].rgProperties[0].colid = DB_NULLID;  
    rgPropSets[0].rgProperties[0].vValue.vt = VT_I4;  
    V_I4(&rgPropSets[0].rgProperties[0].vValue) = DBPROPVAL_UP_CHANGE;  
  
    // Set the rowset properties.  
    hr = pICommandText->QueryInterface(IID_ICommandProperties,  
                            (void **)&pICommandProperties);  
    if (FAILED(hr))  
    {  
        cout << "Failed to get ICommandProperties to set rowset properties.\n";  
        // Release any references and return.  
        goto Exit;  
    } //end if  
    hr = pICommandProperties->SetProperties(cPropSets, rgPropSets);  
    if (FAILED(hr))  
    {  
        cout << "Execute failed to set rowset properties.\n";  
        // Release any references and return.  
        goto Exit;  
    } //end if  
  
    // Execute a command (SELECT * FROM TestISeqStream).  
    hr = pICommandText->SetCommandText(DBGUID_DBSQL,  
                                       L"SELECT * FROM TestISeqStream");  
    if (FAILED(hr))  
    {  
        cout << "Failed to set command text SELECT * FROM.\n";  
        // Release any references and return.  
        goto Exit;  
    } //end if  
  
    hr = pICommandText->Execute(NULL, IID_IRowsetChange, NULL, NULL,  
                                (IUnknown**)&pIRowsetChange);  
    if (FAILED(hr))  
    {  
        cout << "Failed to execute the command SELECT * FROM.\n";  
        // Release any references and return.  
        goto Exit;  
    } //end if  
  
    // Fill the DBBINDINGS array.  
    rgBindings[0].iOrdinal = 2; //ordinal position  
    rgBindings[0].obValue = offsetof(BLOBDATA, pISeqStream);  
    rgBindings[0].obLength = offsetof(BLOBDATA, dwLength);  
    rgBindings[0].obStatus = offsetof(BLOBDATA, dwStatus);  
    rgBindings[0].pTypeInfo = NULL;  
    rgBindings[0].pObject = &ObjectStruct;  
    rgBindings[0].pBindExt = NULL;  
    rgBindings[0].dwPart =  DBPART_VALUE | DBPART_STATUS | DBPART_LENGTH;  
    rgBindings[0].dwMemOwner = DBMEMOWNER_CLIENTOWNED;  
    rgBindings[0].eParamIO = DBPARAMIO_NOTPARAM;  
    rgBindings[0].cbMaxLen = 0;   
    rgBindings[0].dwFlags = 0;  
    rgBindings[0].wType = DBTYPE_IUNKNOWN;  
    rgBindings[0].bPrecision = 0;  
    rgBindings[0].bScale = 0;  
  
    // Create an accessor using the binding information.  
    hr = pIRowsetChange->QueryInterface(IID_IAccessor,   
                                        (void**)&pIAccessor);  
    if (FAILED(hr))  
    {  
        cout << "Failed to get IAccessor interface.\n";  
        // Release any references and return.  
        goto Exit;  
    } //end if  
  
    hr = pIAccessor->CreateAccessor(DBACCESSOR_ROWDATA,  
                                    cBindings,  
                                    rgBindings,   
                                    sizeof(BLOBDATA),  
                                    &hAccessor,  
                                    rgBindStatus);  
    if (FAILED(hr))  
    {  
        cout << "Failed to create an accessor.\n";  
        // Release any references and return.  
        goto Exit;  
    } //end if   
  
    // Now get the first row.  
    hr = pIRowsetChange->QueryInterface(IID_IRowset,   
                                        (void **)&pIRowset);  
    if (FAILED(hr))  
    {  
        cout << "Failed to get IRowset interface.\n";  
        // Release any references and return.  
        goto Exit;  
    } //end if  
  
    hr = pIRowset->GetNextRows(NULL,   
                               0,   
                               1,   
                               &cRowsObtained,   
                               &rghRows);  
  
    hr = pIRowset->GetData(rghRows[0],   
                           hAccessor,   
                           &BLOBGetData);  
  
    // Verify the retrieved data, only if data is not null.  
    if (BLOBGetData.dwStatus == DBSTATUS_S_ISNULL)  
    {  
        // Process null data.  
        cout << "Provider returned a null value.\n";  
    } else if(BLOBGetData.dwStatus == DBSTATUS_S_OK)   
      // Provider returned a nonNULL value.  
    {  
        BLOBGetData.pISeqStream->Read(  
                                    pBuffer,   
                                    cBytes,   
                                    &cBytesRead);  
        if(memcmp(pBuffer, pReadData, cBytes) != 0)  
        {  
            //cleanup   
         }  
  
        SAFE_RELEASE(BLOBGetData.pISeqStream);  
    }  
  
    // Set up data for SetData.  
    pMySeqStream = new CSeqStream();  
  
    /*  
    Put data in to the ISequentialStream object   
    for the provider to write.  
    */  
    pMySeqStream->Write(pWriteData,   
                        cBytes,   
                        NULL);  
  
    BLOBSetData.pISeqStream = (ISequentialStream*)pMySeqStream;  
    BLOBSetData.dwStatus    = DBSTATUS_S_OK;  
    BLOBSetData.dwLength    = pMySeqStream->Length();  
  
    // Set the data.  
    hr = pIRowsetChange->SetData(rghRows[0],   
                                 hAccessor,   
                                 &BLOBSetData);  
        if (FAILED(hr))  
    {  
        cout << "Failed to set data.\n";  
        // Release any references and return.  
        goto Exit;  
    } //end if  
  
    hr = pIAccessor->ReleaseAccessor(hAccessor, NULL);  
    if (FAILED(hr))  
    {  
        cout << "Failed to release accessor.\n";  
        // Release any references and return.  
        goto Exit;  
    } //end if  
    hr = pIRowset->ReleaseRows(cRowsObtained,   
                            rghRows,   
                            NULL,   
                            NULL,   
                            NULL);  
    if (FAILED(hr))  
    {  
        cout << "Failed to release rows.\n";  
        // Release any references and return.  
        goto Exit;  
    } //end if  
Exit:  
    // Free up all allocated memory and release interface pointers.  
  
    CoUninitialize();  
} //end main.  
//..........................................................  
HRESULT GetCommandObject(REFIID riid, IUnknown** ppIUnknown)  
{  
    HRESULT hr = S_OK;  
  
    // Local interface pointers, until a connection is made.  
    IDBInitialize* pIDBInitialize = NULL;  
    IDBProperties*  pIDBProperties = NULL;  
    IDBCreateSession* pIDBCreateSession = NULL;  
    IDBCreateCommand* pIDBCreateCommand = NULL;  
  
    const ULONG cPropSets = 1;  
    DBPROPSET rgPropSets[cPropSets];  
  
    const ULONG cProperties = 4;  
    DBPROP rgProperties[cProperties];  
  
    /*  
    Initialize the property values needed to   
    establish the connection.  
    */  
    for(ULONG i = 0; i < 4; i++)  
        VariantInit(&rgProperties[i].vValue);  
  
    // Server name.  
    rgProperties[0].dwPropertyID = DBPROP_INIT_DATASOURCE;  
    rgProperties[0].vValue.vt = VT_BSTR;  
    rgProperties[0].vValue.bstrVal =   
                    SysAllocString(L"server");  
    rgProperties[0].dwOptions = DBPROPOPTIONS_REQUIRED;  
    rgProperties[0].colid = DB_NULLID;  
  
    // Database.  
    rgProperties[1].dwPropertyID = DBPROP_INIT_CATALOG;  
    rgProperties[1].vValue.vt = VT_BSTR;  
    rgProperties[1].vValue.bstrVal =   
                    SysAllocString(L"pubs");  
    rgProperties[1].dwOptions = DBPROPOPTIONS_REQUIRED;  
    rgProperties[1].colid = DB_NULLID;  
  
    // Username (login).  
    rgProperties[2].dwPropertyID = DBPROP_AUTH_USERID;  
    rgProperties[2].vValue.vt = VT_BSTR;  
    rgProperties[2].vValue.bstrVal =   
                    SysAllocString(L"login");  
    rgProperties[2].dwOptions = DBPROPOPTIONS_REQUIRED;  
    rgProperties[2].colid = DB_NULLID;  
  
    // Password.  
    rgProperties[3].dwPropertyID = DBPROP_AUTH_PASSWORD;  
    rgProperties[3].vValue.vt = VT_BSTR;  
    rgProperties[3].vValue.bstrVal =   
                    SysAllocString(L"password");  
    rgProperties[3].dwOptions = DBPROPOPTIONS_REQUIRED;  
    rgProperties[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.  
    */  
    rgPropSets[0].guidPropertySet   = DBPROPSET_DBINIT;  
    rgPropSets[0].cProperties       = cProperties;  
    rgPropSets[0].rgProperties      = rgProperties;  
  
    // Get the IDBInitialize interface.  
    hr = CoCreateInstance(CLSID_MSOLEDBSQL,   
                            NULL,   
                            CLSCTX_INPROC_SERVER,  
                            IID_IDBInitialize,   
                            (void**)&pIDBInitialize);  
    if(FAILED(hr))  
    {  
        cout << "Failed to get IDBInitialize interface.\n";  
        // Release any references and return.  
        goto Exit;  
  
    } //end if  
  
    // Set initialization properties.  
    hr = pIDBInitialize->QueryInterface(IID_IDBProperties,  
                                        (void **)&pIDBProperties);  
    if(FAILED(hr))  
    {  
        cout << "Failed to get IDBProperties interface.\n";  
        // Release any references and return.  
        goto Exit;  
    } //end if  
  
    hr = pIDBProperties->SetProperties(cPropSets, rgPropSets);  
     if(FAILED(hr))  
    {  
        cout << "Failed to set properties for DBPROPSET_DBINIT.\n";  
        // Release any references and return.  
        goto Exit;  
    } //end if  
  
     hr = pIDBInitialize->Initialize();  
      if(FAILED(hr))  
    {  
        cout << "Failed to initialize.\n";  
        // Release any references and return.  
        goto Exit;  
    } // end if  
  
    //Create a session object.  
      hr = pIDBInitialize->QueryInterface(  
                                IID_IDBCreateSession,  
                                (void **)&pIDBCreateSession);  
       if(FAILED(hr))  
    {  
        cout << "Failed to get pIDBCreateSession interface.\n";  
        // Release any references and return.  
        goto Exit;  
    } // end if  
  
       hr = pIDBCreateSession->CreateSession(  
                                    NULL,   
                                    IID_IDBCreateCommand,  
                                    (IUnknown**)&pIDBCreateCommand);  
     if(FAILED(hr))  
    {  
        cout << "Failed to create session object.\n";  
        // Release any references and return.  
        goto Exit;  
    } // end if  
  
     // Get the CommandText object.  
     hr = pIDBCreateCommand->CreateCommand(  
                                    NULL,   
                                    riid,   
                                    (IUnknown**)ppIUnknown);  
     if(FAILED(hr))  
    {  
        cout << "Failed to create CommandText object.\n";  
        // Release any references and return.  
        goto Exit;  
    } // end if  
  
     return hr;  
Exit:  
    // Free up all allocated memory and release interface pointers.  
     return hr;  
  
} //end function  
//...............................................................  
HRESULT CreateTable(ICommandText* pICommandText)  
{  
    HRESULT hr = S_OK;  
  
    // Drop the xisting table.  
    hr = pICommandText->SetCommandText(  
                            DBGUID_DBSQL,  
                            L"DROP TABLE TestISeqStream");  
    if(FAILED(hr))  
    {  
        cout << "Failed to set command text DROP TABLE.\n";  
        // Release any references and return.  
        goto Exit;  
  
    } //end if  
  
    hr = pICommandText->Execute(NULL, IID_NULL, NULL, NULL, NULL);  
    if(FAILED(hr))  
    {  
        cout << "Failed to drop the table.\n";  
        // Release any references and return.  
        goto Exit;  
    } // end if  
  
    // Create a new table.  
    hr = pICommandText->SetCommandText(DBGUID_DBSQL,  
         L"CREATE TABLE TestISeqStream (col1 int,col2 image)");  
    if(FAILED(hr))  
    {  
        cout << "Failed to set command text CREATE TABLE.\n";  
        // Release any references and return.  
        goto Exit;  
    } // end if  
  
    hr = pICommandText->Execute(NULL, IID_NULL, NULL, NULL, NULL);  
    if(FAILED(hr))  
    {  
        cout << "Failed to create new table.\n";  
        // Release any references and return.  
        goto Exit;  
    } // end if  
  
    // Insert one row into table.  
    hr = pICommandText->SetCommandText(DBGUID_DBSQL,  
    L"INSERT INTO TestISeqStream(col1,col2) VALUES (1,0xAAAAAAAAAAAAAAAAA)");  
    if(FAILED(hr))  
    {  
        cout << "Failed to set command text INSERT INTO.\n";  
        // Release any references and return.  
        goto Exit;  
    } // end if  
  
    hr = pICommandText->Execute(NULL, IID_NULL, NULL, NULL, NULL);  
    if(FAILED(hr))  
    {  
        cout << "Failed to insert record in the table.\n";  
        // Release any references and return.  
        goto Exit;  
    } // end if  
  
Exit:  
    // Free up all allocated memory and release interface pointers.  
     return hr;  
  
} //end function  

См. также

Большие двоичные объекты и объекты OLE
Использование типов больших значений