BCB实现BLOB字段的读写

对于SQL中的TEXT、IMAGE、MEMO字段的存取，可以采用下列程序：
BLOB字段的读取：
TBlobSTream* TemplateStream;
char* TempPlatePtr;              

TemplateStream=new   TBlobStream((TBlobField*)WebQuery->FieldByName
                        ("SearchTem"),bmReadWrite);
TemplatePtr= new char[TemplateStream->Size];
TemplateStream->Read(TemplatePtr, TemplateStream->Size);

BLOB字段的写入：
TBlobSTream* TemplateStream;
char* TempPlatePtr;              

TemplateStream=new   TBlobStream((TBlobField*)WebQuery->FieldByName
                        ("SearchTem"),bmReadWrite);
TemplatePtr= new char[TemplateStream->Size];
TemplateStream->Write(TemplatePtr, TemplateStream->Size);

________________________________________________________________
补充:
获得字段的大小用函数datalength

SQL Server端要作一点设置:
By default, WRITETEXT is a nonlogged operation. This means that  
text or image data is not logged when it is written into the database.  
To use WRITETEXT in its default, nonlogged state,  
//注意!!
the system administrator must use the sp_dboption system stored  
procedure to set select into/bulkcopy,  
//
which allows nonlogged data to be inserted.

做了试验,直接写SQL语句好象不行.
____________________________________________________________________
        一些注意事项和一个例子
在写入时:
(1)如果使用的是TTable,则要将其ReadOnly属性先置为false,然后调用Edit函数;
(2)如果使用的是TQuery,则要将其RequestLive属性先置为true,然后调用Edit函数;
使得TTable(TQuery)是可写的.

下面是一个使用TQuery往content表(主键file_id)中插入一条记录的例子,
script为一个BLOB字段:
   TBlobStream *pScriptStream;
  //插入一条记录
        strSQL1="insert  into  content(file_id,script,key_image) values('";
        strSQL1=strSQL1+m_szFileID+"',null,null)";
        dmStoryEditor->qryExec->SQL->Clear();
        dmStoryEditor->qryExec->SQL->Add(strSQL1);
        dmStoryEditor->qryExec->ExecSQL();
        dmStoryEditor->qryExec->Close();
  //整理要写入的Blob数据   
        LockMemories(NewsScript);
        NewsScript.GetEdition(NewsScript.m_ScriptHead.byteEditionNum);
        NewsScript.m_pScript=(BYTE *)GlobalLock(NewsScript.m_hScript);
        if(NewsScript.m_pScript!=NULL)
        {
   //再将刚插入的记录读出来,使该Query与该条记录关联
        strSQL1="select  file_id,script  from  content  where  file_id='"+
                m_szFileID+"'";
   //允许该Query写
            dmStoryEditor->qryExec->RequestLive=true;
            dmStoryEditor->qryExec->SQL->Clear();
            dmStoryEditor->qryExec->SQL->Add(strSQL1);
            dmStoryEditor->qryExec->Open();
            dmStoryEditor->qryExec->First();
   //将该Query置为可写
            dmStoryEditor->qryExec->Edit();
            pScriptStream=new   TBlobStream((TBlobField*)dmStoryEditor->
                                qryExec->FieldByName("script"),bmReadWrite);
            pScriptStream->Write(NewsScript.m_pScript,  
                                        NewsScript.m_lScriptRealSize);
            dmStoryEditor->qryExec->Post();
            dmStoryEditor->qryExec->RequestLive=false;
            delete pScriptStream;
       }
       GlobalUnlock(NewsScript.m_hScript);
       UnLockMemories(NewsScript);