如何避免 SAS 覆盖我的数据集..." - 如果您的意思是在记录级别覆盖 - 检查 _iorc_ 值会让你控制做什么.您可以添加自己的逻辑来更新下面的模板代码.不匹配的值为_DSENMR".

"How can I avoid SAS to overwrite my dataset..." - if you mean overwriting on record level - checking _iorc_ value will give you control on what to do. You can add own logic to updates to the template code below. Value for Not matched is "_DSENMR".

data have_1;
modify have_1 have_2(where=(message="X")) updatemode=nomissingcheck;
by reference;

    if      _iorc_ = %sysrc(_SOK) then do;
      * Update row ;
      replace;
    end;
    else if _iorc_ = %sysrc(_DSENMR) then do;
      * Add row ;
      output;
      _error_ = 0;
    end;
    else if _iorc_ = %sysrc(_DSEMTR) then do;
      * Multiple TRANSACTION data set observations do ;
      * not exist in MASTER data set ;
      _error_ = 0;
    end;
    else if _iorc_ = %sysrc(_DSENOM) then do;
      * No matching observation was found in MASTER data set ;
      _error_ = 0;
    end;
  run;

在此处查看更多信息 http://support.sas.com/documentation/cdl/en/basess/58133/HTML/default/viewer.htm