请教VC ADO 如何对ORACLE的CLOB操作

Question

如题，重谢50分

Answer 1

用ado连接oracle读取大数据量字段：
long lSize = m_pRecordset->Fields->Item["data"]->ActualSize; //data是你的Clob字段
while(lSize>0)
{
　lIsRead= lSize >=ChunkSize?ChunkSize:lSize;
　//从字段data中获取一个数据包
　varChunk = m_pRecordset->Fields->Item["data"]->GetChunk(lIsRead);
　for(index=0;index＜LISREAD;INDEX++)
　　::SafeArrayGetElement(varChunk.parray，&index，buf+index);
　　//将数据包写入文件
　　f.Write(buf，lIsRead);
　　lSize -=lIsRead;
} 

Answer 2

详情参考：
$oracle\ora90\oo4o\CPP\WORKBOOK\LOB   目录里的   CLOBREAD.CPP

Answer 3

供参考：
_CommandPtr   pCommand;  
  _ParameterPtr   pParam1; //将要包含BLOB的参数  
  CString   sQuery; //SQL语句  
  _variant_t   vRecsAffected(0L);  
   
  _variant_t   vNull; //填充用  
  vNull.vt   =   VT_ERROR;  
  vNull.scode   =   DISP_E_PARAMNOTFOUND;  
   
   
  sQuery.Format("INSERT   INTO   EMP_PHOTO   VALUES   (   '%s',   'bitmap',   ?   )",   sEmpNo   );  
   
  _RecordsetPtr   pRs;  
  try  
  {  
  HRESULT   hr   =   pCommand.CreateInstance(__uuidof(Command));  
  if(FAILED(hr))   throw("Unable   to   create   Command   object");  
   
  //得到command对象  
  pCommand->PutRefActiveConnection(m_pConnection);  
   
  //开始查询  
  pCommand->PutCommandText((LPCTSTR)   sQuery);  
   
  //说明是sql语句查询  
  pCommand->PutCommandType(adCmdText);  
   
  //初始化parameter对象  
  hr   =   pParam1.CreateInstance(__uuidof(Parameter));  
  if   (FAILED(hr))   throw   ("Unable   to   create   Parameter   object");  
   
  //制造blob参数  
  pParam1   =   pCommand->CreateParameter((LPCTSTR)   "picture",   adBinary,   adParamInput,   vBLOB.parray->rgsabound[0].cElements,   vBLOB);  
   
  //将此参数加入command的参数集合  
  hr   =   pCommand->Parameters->Append(pParam1);  
  if   (FAILED(hr))   throw   ("Unable   to   append   Parameter   to   Command   Object");  
   
   
  hr   =   pCommand->Execute(&vRecsAffected,   &vNull,   adCmdText);  
  if   (FAILED(hr))   throw   ("Failed   to   insert   BLOB   into   Database");  
  }  
  catch(_com_error   &e)  
  {  
  DisplayError(e);  
  return   0;  
  }  
   
  表结构为：  
   
  id   number(3),  
  imeage_type   varchar2(20),  
  image   blob.   

Answer 4

利用AppendChunk  和  GetChunk   方法进行操作
#import   "C:\Program   Files\Common   Files\System\ADO\msado15.dll"           no_namespace   rename("EOF",   "EndOfFile")  
  #define   ChunkSize       100  
  #include   <ole2.h>  
  #include   <stdio.h>  
  #include   "conio.h"  
  #include   "malloc.h"  
  #include   "AppendChunkX.h"  
  inline   void   TESTHR(HRESULT   x)   {if   FAILED(x)   _com_issue_error(x);};  
  void   AppendChunkX(void);  
  void   PrintProviderError(_ConnectionPtr   pConnection);  
  void   main()  
  {  
          if(FAILED(::CoInitialize(NULL)))  
                  return;  
          AppendChunkX();  
          ::CoUninitialize();  
  }  
  void     AppendChunkX(void)  
  {  
          _RecordsetPtr   pRstPubInfo   =   NULL;  
          _ConnectionPtr   pConnection   =   NULL;  
          IADORecordBinding       *picRs   =   NULL;      
          CPubInfoRs   pubrs;                     //C++   class   object        
   
          HRESULT   hr   =   S_OK;  
          _bstr_t   strCnn("Provider=sqloledb;Data   Source=srv;"  
                  "Initial   Catalog=Pubs;User   Id=sa;Password=;");  
          _bstr_t   strMessage,strPubID,strPRInfo;  
          _variant_t   varChunk;  
          long   lngOffSet,lngLogoSize;  
          char   pubId[50];  
          lngOffSet   =   0;          
          UCHAR   chData;  
          CHAR   ch;  
          SAFEARRAY   FAR   *psa;  
          SAFEARRAYBOUND   rgsabound[1];  
          rgsabound[0].lLbound   =   0;  
          rgsabound[0].cElements   =   ChunkSize;  
          try  
          {  
                  TESTHR(pConnection.CreateInstance(__uuidof(Connection)));  
                  TESTHR(pConnection->Open(strCnn,"","",NULL));  
                  TESTHR(hr=   pRstPubInfo.CreateInstance(__uuidof(Recordset)));      
                  pRstPubInfo->CursorType   =   adOpenKeyset;  
                  pRstPubInfo->LockType   =   adLockOptimistic;  
                  TESTHR(pRstPubInfo->Open("pub_info",  
                          _variant_t((IDispatch*)pConnection,true),  
                          adOpenKeyset,adLockOptimistic,adCmdTable));  
                  TESTHR(pRstPubInfo->QueryInterface(  
                          __uuidof(IADORecordBinding),(LPVOID*)&picRs));  
                  TESTHR(picRs->BindToRecordset(&pubrs));  
                  strMessage   =   "Available   logos   are:   "   +   (_bstr_t)"\n\n";  
                  printf(strMessage);  
                  int   Counter   =   0;  
                  while(!(pRstPubInfo->EndOfFile))  
                  {    
                          printf("\n%s",pubrs.m_sz_pubid);  
                          printf("\n%s",strtok(pubrs.m_sz_prinfo,","));  
   
                          //Display   5   records   at   a   time   and   wait   for   user   to   continue.  
                          if   (++Counter   >=   5)  
                          {  
                                  Counter   =   0;  
                                  printf("\nPress   any   key   to   continue...");  
                                  getch();  
                          }  
                          pRstPubInfo->MoveNext();    
                  }  
   
                  //Prompt   For   a   Logo   to   Copy  
                  printf("\nEnter   the   ID   of   a   logo   to   copy:   ");  
                  scanf("%s",pubId);  
                  strPubID   =   pubId;  
   
                  //Copy   the   logo   to   a   variable   in   chunks  
                  pRstPubInfo->Filter   =   "pub_id   =   '"     +   strPubID   +   "'";  
                  lngLogoSize   =   pRstPubInfo->Fields->Item["logo"]->ActualSize;  
   
                  //Create   a   safe   array   to   store   the   array   of   BYTES      
                  rgsabound[0].cElements   =   lngLogoSize;  
                  psa   =   SafeArrayCreate(VT_UI1,1,rgsabound);  
   
                  long   index1   =   0;  
                  while(lngOffSet   <   lngLogoSize)  
                  {  
                          varChunk   =   pRstPubInfo->Fields->  
                                                  Item["logo"]->GetChunk(ChunkSize);  
   
                          //Copy   the   data   only   up   to   the   Actual   Size   of   Field.      
                          for(long   index=0;index<=(ChunkSize-1);index++)  
                          {  
                                  hr=   SafeArrayGetElement(varChunk.parray,&index,&chData);  
                                  if(SUCCEEDED(hr))  
                                  {  
                                          //Take   BYTE   by   BYTE   and   advance   Memory   Location  
                                          TESTHR(SafeArrayPutElement(psa,&index1,&chData));  
                                          index1++;  
                                  }  
                                  else  
                                          break;  
                          }  
                          lngOffSet   =   lngOffSet   +   ChunkSize;  
                  }  
                  lngOffSet   =   0;  
   
                  printf("Enter   a   new   Pub   Id:   ");  
                  scanf("%s",pubrs.m_sz_pubid);  
                  strPubID   =   pubrs.m_sz_pubid;  
   
                  printf("Enter   descriptive   text:   "   );  
                  scanf("%c",&ch);  
                  gets(pubrs.m_sz_prinfo);  
   
                  //   Temporarily   add   new   publisher   to   table   to   avoid   error   due      
                  //   to   foreign   key   constraint.  
                  pConnection->Execute("INSERT   publishers(pub_id)   VALUES('"   +    
                          strPubID   +   "')",NULL,adCmdText);  
                   
                  pRstPubInfo->AddNew();  
                  pRstPubInfo->Fields->GetItem("pub_id")->PutValue(strPubID);  
                  pRstPubInfo->Fields->GetItem("pr_info")->  
                          PutValue(pubrs.m_sz_prinfo);  
   
                  //Assign   the   Safe   array     to   a   variant.    
                  varChunk.vt   =   VT_ARRAY|VT_UI1;  
                  varChunk.parray   =   psa;  
                  hr   =   pRstPubInfo->Fields->GetItem("logo")->  
                                  AppendChunk(varChunk);    
   
                  //Update   the   table    
                  pRstPubInfo->Update();  
   
                  lngLogoSize   =   pRstPubInfo->Fields->Item["logo"]->ActualSize;  
   
                  //Show   the   newly   added   record.  
                  printf("New   Record   :   %s\nDescription   :   %s\nLogo   Size   :   %s\n",  
                          pubrs.m_sz_pubid,  
                          pubrs.m_sz_prinfo,(LPCSTR)(_bstr_t)pRstPubInfo->Fields->  
                          Item["logo"]->ActualSize);  
   
                  //Delete   new   records   because   this   is   demonstration.  
                  pConnection->Execute("DELETE   FROM   PUB_INFO   WHERE   pub_id   =   '"  
                                                  +   strPubID   +"'",NULL,adCmdText);  
   
                  pConnection->Execute("DELETE   FROM   publishers   WHERE   pub_id   =   '"  
                                                  +   strPubID   +"'",NULL,adCmdText);  
   
                  pRstPubInfo->Close();  
                  pConnection->Close();  
          }  
          catch(_com_error   &e)  
          {  
                  //   Notify   the   user   of   errors   if   any.  
                  _bstr_t   bstrSource(e.Source());  
                  _bstr_t   bstrDescription(e.Description());  
   
                  PrintProviderError(pConnection);  
                  printf("Source   :   %s   \n   Description   :   %s\n",  
                                  (LPCSTR)bstrSource,(LPCSTR)bstrDescription);  
          }  
  }  
   
   
  void   PrintProviderError(_ConnectionPtr   pConnection)  
  {  
          //   Print   Provider   Errors   from   Connection   object.  
          //   pErr   is   a   record   object   in   the   Connection's   Error   collection.  
          ErrorPtr     pErr       =   NULL;  
          long             nCount   =   0;          
          long             i             =   0;  
   
          if(   (pConnection->Errors->Count)   >   0)  
          {  
                  nCount   =   pConnection->Errors->Count;  
                  //   Collection   ranges   from   0   to   nCount   -1.  
                  for(i   =   0;   i   <   nCount;   i++)  
                  {  
                          pErr   =   pConnection->Errors->GetItem(i);  
                          printf("\t   Error   number:   %x\t%s",   pErr->Number,  
                                  (LPCSTR)   pErr->Description);  
                  }  
          }  
  }  
   
  AppendChunkX.h:  
   
  #include   "icrsint.h"  
   
  //This   Class   extracts   pubid,prinfo.  
   
  class   CPubInfoRs   :   public   CADORecordBinding  
  {  
          BEGIN_ADO_BINDING(CPubInfoRs)  
   
          ADO_VARIABLE_LENGTH_ENTRY2(1,   adVarChar,   m_sz_pubid,    
                    sizeof(m_sz_pubid),   l_pubid,   TRUE)  
   
          ADO_VARIABLE_LENGTH_ENTRY2(3,   adVarChar,   m_sz_prinfo,    
                    sizeof(m_sz_prinfo),   l_prinfo,   TRUE)  
   
          END_ADO_BINDING()  
   
  public:  
          CHAR       m_sz_pubid[10];  
          ULONG     l_pubid;  
          CHAR       m_sz_prinfo[200];  
          ULONG   l_prinfo;          
   
  };   

Answer 5

上述方法都试过了，行不通，再求方法，感谢zhangwonderful