将二进制数据导出本地文件

　　将文件以二进制文件的形式存放到数据库中，需要时再将其导出来，首先看下实现代码：

方法1：直接以文件形式导出：

Procedure ExportAttachment(AdoConn: TADOConnection);
var
  pAdoQry: TADOQuery;
  sSQL, sFileName: string;
begin
  pAdoQry := TADOQuery.Create(nil);
  pAdoQry.Connection := AdoConn;
  
  try
    sSQL := 'SELECT * FROM TUXKNR';
    if not OpenSQL(pAdoQry, sSQL) then Exit; // OpenSQL：公共函数

    sFileName := 'D:	mp	mp.dwg';
    if FileExists(sFileName) then
      DeleteFile(sFileName);
      
    if pAdoQry.FieldByName('TUNR').IsNull then Exit;
    TBlobField(pAdoQry.FieldByName('TUNR')).SaveToFile(sFileName);  // TBlobField /r:DB
  finally
    FreeAndNil(pAdoQry);
  end;          
end;

 方法2：以流的形式导出： 

Procedure ExportAttachment(AdoConn: TADOConnection);
var
  pAdoQry: TADOQuery;
  pStream: TMemoryStream;   //r:classes
  pJpg: TJPEGImage;         //r:jpeg
  sSQL: string;
begin
  pAdoQry := TADOQuery.Create(nil);
  pAdoQry.Connection := AdoConn;
  
  try
    sSQL := 'SELECT * FROM TUXKNR';
    if not OpenSQL(pAdoQry, sSQL) then Exit; // OpenSQL：公共函数
      
    if pAdoQry.FieldByName('TUNR').IsNull then Exit;

    pStream:= TMemoryStream.Create;
    pJpg := TJPEGImage.Create;
    try
      TBlobField(pAdoQry.FieldByName('TUNR')).SaveToStream(pStream);
      pStream.Position := 0;
      pJpg.LoadFromStream(pStream);
      imgSign.Picture.Assign(pJpg); // imgSign：图片控件（为了显示效果）
    finally
      pJpg.Free;
      pStream.Free;
    end;
  finally
    FreeAndNil(pAdoQry);
  end;          
end;