Safely Merging Many Datasets

如题，该代码摘自“Safely Merging Many Datasets”一文，可以下载原文http://support.sas.com/resources/papers/proceedings11/409-2011.pdf

/********************************************************
A macro to safely merge all datasets in a libraryby 
renaming and relabeling variables that sharenames.
********************************************************/

/* Open the macro */
%macro merge_library;

/* Assign the libref */
libname tomerge 'path/to/datasets';

/* Assign the merge by variable to mergeby macro variable */
%let mergeby=var_name;

/* Get all memnames as macro variables */
proc sql noprint;
     select distinct memname,count(distinct memname) 
            into:ds1 - :ds999, 
                :dsnum
     from dictionary.columns

     where libname='TOMERGE' and memname~='MERGED_DATA';
quit;

/* DO loop for each dataset */
%do i=1 %to &dsnum;

   /* Sort by mergeby variable */
   proc sort data=tomerge.&&ds&i;
        by &mergeby;
   run;

   /* Select duplicate variable names in the current dataset */
   proc sql noprint;
        select
            trim(name)||'='||left(trim(name))||"_&i",
            trim(name)||'='||"'"||left(trim("&&ds&i"))||":"
               ||left(trim(compress(label,"'")))||"'"
            into :rename1 - :rename99999, 
                 :relabel1 - :relabel99999 
        from 
            (select distinct name, memname, label
                  from dictionary.columnswhere 
                       libname=upcase("tomerge") and memname=upcase("&&dS&i")and not
                       indexw(upcase("&mergeby"),upcase(name))and upcase(name) in
                          (select upcase(name)from dictionary.columnswhere 
                               libname=upcase("tomerge") and memname ne upcase("&&ds&i")));
   quit;

/* Store number of duplicate variables as a macro variable */
   %let renamenum = &sqlobs;

/* Make a copy and execute rename/label statements */
   data copy_&i;
      set tomerge.&&ds&i;
      %if &renamenum > 0 %then %do;
          %do q=1 %to &renamenum;
           rename &&rename&q;
           label &&relabel&q;
          %end;
      %end;
   run;

/* Special case for the first merge */
   %if &i~=1 and &i=2 %then %do;
      data tomerge.merged_data;
         retain &mergeby;
         merge copy_1 copy_&i;
         by &mergeby;
   run;
   %end;

/* Regular case for all subsequent merges */
   %else %if &i~=1 %then %do;
      data tomerge.merged_data;
         retain &mergeby;
         merge tomerge.merged_data copy_&i;
         by &mergeby;
      run;
   %end;

   %put &i &&ds&i;

/* End DO loop */
%end;

/* Close the Macro */
%mend merge_library;
/* Call the macro */
%merge_library;