Set Large Data (Native Client OLE DB-provider)

van toepassing op:SQL Server Azure SQL Database Azure SQL Managed Instance Azure Synapse Analytics Analytics Platform System (PDW)

Dit voorbeeld laat zien hoe je BLOB-data kunt instellen, een tabel kunt maken, een voorbeeldrecord kunt toevoegen, dat record in de rijset kunt ophalen en vervolgens de waarde van het BLOB-veld kunt instellen. Dit voorbeeld wordt niet ondersteund op IA64.

Om een pointer naar zijn eigen storage object door te geven, maakt de consument een accessor aan die de waarde van de BLOB-kolom bindt en vervolgens de IRowsetChange::SetData- of IRowsetChange::InsertRow-methoden aanroept.

De codevoorbeelden in dit artikel gebruiken de AdventureWorks2025 of AdventureWorksDW2025 voorbeelddatabase die u kunt downloaden van de startpagina van Microsoft SQL Server Samples en Community Projects .

Belangrijk

Gebruik waar mogelijk Windows-verificatie. Als Windows-authenticatie niet beschikbaar is, vraag gebruikers dan om hun inloggegevens tijdens runtime in te voeren. Vermijd het opslaan van inloggegevens in een bestand. Als je inloggegevens moet behouden, moet je ze versleutelen met de Win32 crypto API.

Procedures

Om BLOB-gegevens in te stellen

Maak een DBOBJECT-structuur die beschrijft hoe de kolom BLOB benaderd moet worden. Stel het dwFlag-element van de DBOBJECT-structuur in op STGM_READ en stel het iid-element in op IID_ISequentialStream (de interface die blootgesteld moet worden).
Stel de eigenschappen in de DBPROPSET_ROWSET property-groep zodat de rowset updateerbaar is.
Maak een set bindings aan (één van elke kolom) door gebruik te maken van een array van DBBINDING-structuren. Stel het wType-element in de DBBINDING-structuur in op DBTYPE_IUNKNOWN, en het pObject-element om te verwijzen naar de DBOBJECT-structuur die je hebt gemaakt.
Maak een accessor aan met behulp van de bindingsinformatie in de DBBINDINGS-array van structuren.
Bel GetNextRows om de volgende rijen in de rowset te halen. Roep GetData aan om de gegevens uit de rowset te lezen.
Om de data in te stellen, maak je een opslagobject dat de data bevat (en ook de lengte-indicator), en roep vervolgens IRowsetChange::SetData (of IRowsetChange::InsertRow) aan met de accessor die de BLOB-kolom bindt.

Example

Description

Compileer met ole32.lib oleaut32.lib en voer de volgende C++-codevermelding uit. Deze applicatie maakt verbinding met de standaard SQL Server-instantie van je computer. Op sommige Windows-besturingssystemen moet je (localhost) of (local) veranderen naar de naam van je SQL Server-instantie. Om verbinding te maken met een benoemde instantie, verander je de verbindingsstring van L"(local)" naar L"(local)\\name", waarbij de naam de genoemde instantie is. Standaard wordt SQL Server Express geïnstalleerd op een benoemde instantie. Zorg ervoor dat je INCLUDE-omgevingsvariabele de map bevat die sqlncli.h bevat.

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