用BCB如何向Oracle8.0.5中更新BLOB

[anglebird]

采用BDE，如何向Oracle中更新BLOB，最好有源程序。

[garypeng]

摘自水木清华站：

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);

[luhongjun]

http://www.csdn.net/expert/topic/152/152613.shtm

[fenglingdu]

关注。。。

[zygtp]

用TClientDataSet有时不行