Set Large Data (Native Client OLE DB provider)

platí pro:SQL Server Azure SQL Database Azure SQL Managed Instance Azure Synapse Analytics Analytický platformní systém (PDW)

Tato ukázka ukazuje, jak nastavit data BLOB, vytvořit tabulku, přidat ukázkový záznam, načíst tento záznam ve shodě řádků a poté nastavit hodnotu pole BLOB. Tento vzorek není na IA64 podporován.

Pro předání ukazatele na svůj vlastní objekt úložiště uživatel vytvoří přístupový modul, který naváže hodnotu sloupce BLOB a poté volá metody IRowsetChange::SetData nebo IRowsetChange::InsertRow .

Ukázky kódu v tomto článku používají ukázkovou databázi AdventureWorks2025 nebo AdventureWorksDW2025, kterou si můžete stáhnout z domovské stránky Microsoft SQL Serveru pro ukázky a komunitní projekty .

Důležité

Pokud je to možné, použijte ověřování systému Windows. Pokud není možné Windows Authentication, vyzvejte uživatele k zadání přihlašovacích údajů během běhu. Vyhněte se ukládání přihlašovacích údajů do souboru. Pokud musíte zachovat přihlašovací údaje, měli byste je zašifrovat pomocí kryptografického API Win32.

Procedures

Pro nastavení BLOB dat

Vytvořte strukturu DBOBJECT, která popisuje, jak by měl být sloupec BLOB přístupný. Nastavte prvek dwFlag ve struktuře DBOBJECT na STGM_READ a iid prvek na IID_ISequentialStream (rozhraní, které má být vystaveno).
Nastavte vlastnosti ve skupině DBPROPSET_ROWSET tak, aby byla řádka aktualizovatelná.
Vytvořte sadu bindingů (jednu z každého sloupce) pomocí pole struktur DBBINDING. Nastavte element wType ve struktuře DBBINDING na DBTYPE_IUNKNOWN a prvek pObject , aby ukazoval na strukturu DBOBJECT, kterou jste vytvořili.
Vytvořte accessor pomocí vazebních informací v poli struktur DBBINDINGS.
Zavolejte GetNextRows pro načtení dalších řádků do sady řádků. Zavolejte GetData , abyste přečetli data z řádkové sady.
Pro nastavení dat vytvořte úložný objekt obsahující data (a také indikátor délky) a poté zavolejte IRowsetChange::SetData (nebo IRowsetChange::InsertRow) s přístupem, který váže sloupec BLOB.

Example

Description

Zkompilujte pomocí ole32.lib oleaut32.lib a spusťte následující C++ kódový seznam. Tato aplikace se připojuje k výchozí instanci SQL Serveru vašeho počítače. Na některých Windows operačních systémech budete muset změnit (localhost) nebo (local) na název instance SQL Serveru. Pro připojení k pojmenované instanci změňte spojovací řetězec z L"(local)" na L"(local)\\name", kde název je pojmenovaná instance. Ve výchozím nastavení se SQL Server Express instaluje do pojmenované instance. Ujistěte se, že vaše proměnná INCLUDE zahrnuje adresář, který obsahuje sqlncli.h.

Code

// compile with: ole32.lib oleaut32.lib  
#define UNICODE  
#define DBINITCONSTANTS  
#define INITGID  
#define OLEDBVER 0x0250  // to include correct interfaces  
  
#include <windows.h>  
#include <stdio.h>  
#include <stddef.h>  
#include <iostream>  
#include <oledb.h>  
#include <oledberr.h>  
#include <SQLNCLI.h>  
  
using namespace std;  
  
#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);  
  
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() {  
   return ++m_cRef;  
}  
  
ULONG CSeqStream::Release() {  
   // 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(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((void*)((BYTE*)m_pBuffer + m_iPos), pv, cb);  
   // m_iPos += cb;  
  
   if (pcbWritten)  
      *pcbWritten = cb;  
  
   return S_OK;  
}  
  
int main() {  
   CoInitialize(NULL);  
  
   DBOBJECT ObjectStruct;  
   ObjectStruct.dwFlags = STGM_READ;  
   ObjectStruct.iid = IID_ISequentialStream;  
  
   struct BLOBDATA {  
      DBSTATUS dwStatus;     
      DBLENGTH 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;  
  
   DBCOUNTITEM 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 Command object  
   hr = GetCommandObject(IID_ICommandText, (IUnknown**)&pICommandText);  
   if (FAILED(hr)) {  
      printf("Failed to get ICommandText interface.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   // Create table with image column and index  
   hr = CreateTable(pICommandText);  
   if (FAILED(hr)) {  
      printf("Failed to create table.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   // 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)) {  
      printf("Failed to get ICommandProperties to set rowset properties.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   hr = pICommandProperties->SetProperties(cPropSets, rgPropSets);  
  
   if (FAILED(hr)) {  
      printf("Execute failed to set rowset properties.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   // Execute a command (SELECT * FROM TestISeqStream)  
   hr = pICommandText->SetCommandText(DBGUID_DBSQL, L"SELECT * FROM TestISeqStream");  
  
   if (FAILED(hr)) {  
      printf("Failed to set command text SELECT * FROM.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   hr = pICommandText->Execute(NULL,   
      IID_IRowsetChange,   
      NULL,   
      NULL,  
      (IUnknown**)&pIRowsetChange);  
  
   if (FAILED(hr)) {  
      printf("Failed to execute the command SELECT * FROM.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   // 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)) {  
      printf("Failed to get IAccessor interface.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   hr = pIAccessor->CreateAccessor(DBACCESSOR_ROWDATA,  
      cBindings,  
      rgBindings,   
      sizeof(BLOBDATA),  
      &hAccessor,  
      rgBindStatus);  
  
   if (FAILED(hr)) {  
      printf("Failed to create an accessor.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   // get the first row.  
   hr = pIRowsetChange->QueryInterface(IID_IRowset, (void **)&pIRowset);  
   if (FAILED(hr)) {  
      printf("Failed to get IRowset interface.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   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  
      printf("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 into 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))     {  
      printf("Failed to set data.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   hr = pIAccessor->ReleaseAccessor(hAccessor, NULL);  
   if (FAILED(hr)) {  
      printf("Failed to release accessor.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   hr = pIRowset->ReleaseRows(cRowsObtained, rghRows, NULL, NULL, NULL);  
  
   if (FAILED(hr)) {  
      printf("Failed to release rows.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
Exit:  
   // Release all allocated memory and release interface pointers.  
   CoUninitialize();  
}  
  
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 property values needed to establish 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"(local)");  
   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"AdventureWorks");  
   rgProperties[1].dwOptions = DBPROPOPTIONS_REQUIRED;  
   rgProperties[1].colid = DB_NULLID;  
  
   rgProperties[2].dwPropertyID = DBPROP_AUTH_INTEGRATED;  
   rgProperties[2].vValue.vt = VT_BSTR;  
   rgProperties[2].vValue.bstrVal = SysAllocString(L"SSPI");  
   rgProperties[2].dwOptions = DBPROPOPTIONS_REQUIRED;  
   rgProperties[2].colid = DB_NULLID;  
  
   // Properties are now set.  Next, construct DBPROPSET structure (rgInitPropSet) 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_SQLNCLI11,   
      NULL,   
      CLSCTX_INPROC_SERVER,  
      IID_IDBInitialize,   
      (void**)&pIDBInitialize);  
  
   if (FAILED(hr)) {  
      printf("Failed to get IDBInitialize interface.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   // Set initialization properties.  
   hr = pIDBInitialize->QueryInterface(IID_IDBProperties, (void **)&pIDBProperties);  
   if (FAILED(hr)) {  
      printf("Failed to get IDBProperties interface.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   hr = pIDBProperties->SetProperties(cPropSets, rgPropSets);  
   if (FAILED(hr)) {  
      printf("Failed to set properties for DBPROPSET_DBINIT.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   hr = pIDBInitialize->Initialize();  
   if (FAILED(hr)) {  
      printf("Failed to initialize.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   // Create a session object.  
   hr = pIDBInitialize->QueryInterface( IID_IDBCreateSession,  
                                        (void **)&pIDBCreateSession);  
  
   if (FAILED(hr)) {  
      printf("Failed to get pIDBCreateSession interface.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   hr = pIDBCreateSession->CreateSession( NULL, IID_IDBCreateCommand, (IUnknown**)&pIDBCreateCommand);  
  
   if (FAILED(hr)) {  
      printf("Failed to create session object.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   // Get CommandText object  
   hr = pIDBCreateCommand->CreateCommand( NULL, riid, (IUnknown**)ppIUnknown);  
  
   if (FAILED(hr)) {  
      printf("Failed to create CommandText object.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   return hr;  
  
Exit:  
   // Free up all allocated memory and release interface pointers.  
   return hr;  
}  
  
HRESULT CreateTable(ICommandText* pICommandText) {  
   HRESULT hr = S_OK;  
  
   // drop the table "TestISeqStream" if the table exists.  
   hr = pICommandText->SetCommandText( DBGUID_DBSQL, L"if object_id('TestISeqStream') is not null drop table TestISeqStream");  
   if (FAILED(hr)) {  
      printf("Failed to set command text DROP TABLE.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   hr = pICommandText->Execute(NULL, IID_NULL, NULL, NULL, NULL);  
   if (FAILED(hr)) {  
      printf("Failed to drop the table.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   // Create a new table.  
   hr = pICommandText->SetCommandText(DBGUID_DBSQL,   
      L"CREATE TABLE TestISeqStream (col1 int,col2 image)");  
  
   if (FAILED(hr)) {  
      printf("Failed to set command text CREATE TABLE.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   hr = pICommandText->Execute(NULL, IID_NULL, NULL, NULL, NULL);  
   if (FAILED(hr)) {  
      printf("Failed to create table.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   // Insert one row into table.  
   hr = pICommandText->SetCommandText(DBGUID_DBSQL,  
      L"INSERT INTO TestISeqStream(col1,col2) VALUES (1,0xAAAAAAAAAAAAAAAAA)");  
   if (FAILED(hr)) {  
      printf("Failed to set command text INSERT INTO.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
   hr = pICommandText->Execute(NULL, IID_NULL, NULL, NULL, NULL);  
  
   if (FAILED(hr)) {  
      printf("Failed to insert record in the table.\n");  
      // Release any references and return.  
      goto Exit;  
   }  
  
Exit:  
   // Release all allocated memory and release interface pointers.  
   return hr;  
}

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Last updated on 2025-11-19