设置大型数据（本机客户端 OLE DB 访问接口）

项目
07/04/2024

适用于：SQL Server Azure SQL 数据库 Azure SQL 托管实例 Azure Synapse Analytics Analytics 平台系统（PDW）

此示例显示如何设置 BLOB 数据、创建表、添加示例记录、从行集中提取该记录，然后设置该 BLOB 字段的值。 IA64 平台不支持此示例。

为了将指针传递给它自己的存储对象，使用者创建一个绑定 BLOB 列的值的取值函数，然后调用 IRowsetChange::SetData 或 IRowsetChange::InsertRow 方法。

本文中的 Transact-SQL 代码示例使用 AdventureWorks2022 或 AdventureWorksDW2022 示例数据库，可从 Microsoft SQL Server 示例和社区项目主页下载它。

重要

请尽可能使用 Windows 身份验证。如果 Windows 身份验证不可用，请在运行时提示用户输入其凭据。不要将凭据存储在一个文件中。如果必须保存凭据，应当用 Win32 crypto API（Win32 加密 API）加密它们。

过程

设置 BLOB 数据

创建一个描述应如何访问 BLOB 列的 DBOBJECT 结构。将 DBOBJECT 结构的 dwFlag 元素设置为 STGM_READ，并将 iid 元素设置为 IID_ISequentialStream（要公开的接口）。
设置 DBPROPSET_ROWSET 属性组中的属性，以使行集可更新。
通过使用 DBBINDING 结构数组创建一组绑定（每列一个）。将 DBBINDING 结构中的 wType 元素设置为 DBTYPE_IUNKNOWN，并将 pObject 元素设置为指向创建的 DBOBJECT 结构。
使用 DBBINDINGS 结构数组中的绑定信息创建取值函数。
调用 GetNextRows 将后续的行提取到行集中。调用 GetData 以读取行集中的数据。
若要设置数据，创建一个存储对象（其中包含数据以及长度指示器），然后通过绑定 BLOB 列的取值函数调用 IRowsetChange::SetData（或 IRowsetChange::InsertRow）。

示例

说明

使用 ole32.lib 和 oleaut32.lib 编译并执行以下 C++ 代码列表。此应用程序连接到您的计算机上默认的 SQL Server 实例。在某些 Windows 操作系统上，您需要将 (localhost) 或 (local) 更改为您的 SQL Server 实例的名称。要连接到命名实例，请将连接字符串从 L"(local)" 更改为 L"(local)\\name"，其中 name 是命名实例。默认情况下，SQL Server Express 安装在命名实例中。请确保 INCLUDE 环境变量包含包含 sqlncli.h 的目录。

代码

// 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;  
}

通过

设置大型数据（本机客户端 OLE DB 访问接口）

过程

设置 BLOB 数据

示例

说明

代码

反馈

其他资源