SAS Reverse Column Order

Question

Issue:

I'm looking to reverse the order of all columns in a sas dataset. Should I achieve this by first transposing and then using a loop to reverse the order of the columns? This is my logic...

Step One:

data pre_transpose; 
            set sashelp.class;
            *set &&dataset&i.. ;    
                _row_ + 1;              * Unique identifier ;
                length _charvar_ $20;   * Create 1 character variable ;
            run; 

Step One Output:

Step Two: Do I Reverse Columns Here?

proc transpose data = pre_transpose out = middle (where = (lowcase(_name_) ne '_row_'));
                by _row_;
                var _all_;
            quit; 

Step Two Output:

EDIT:

I have attempted this:

/* use proc sql to create a macro variable for column names */ 
            proc sql noprint; 
                select varnum, nliteral(name) 
                into :varlist, :varlist separated by ' '
                from dictionary.columns
                where libname = 'WORK' and memname = 'all_character'
                order by varnum desc;
            quit;

            /* Use retain to maintain format */ 
            data reverse_columns;
            retain &varlist.;
            set all_character;
            run;        

But I did not achieve the results I was looking for - the column order is not reversed. 

Answer 1

You just need to get the list of variable names. One way is to use the metadata. Do if your dataset is member HAVE in libref WORK then you could use this to get the list of variable names into a single macro variable.

proc sql noprint;
  select varnum , nliteral(name)
    into :varlist, :varlist separated by ' ' 
  from dictionary.columns
  where libname='WORK' and memname='HAVE'
  order by varnum desc 
  ;
quit;

You could then use the macro variable in a data step like this.

data want ;
   retain &varlist ;
   set have ;
run;

Note that the value of libname and memname in DICTIONARY.COLUMNS is in uppercase only.