CODEWITHSUNDEEP
if-statementsasexists
Giuseppe
Giuseppe

Reputation: 507

SAS: update dataset if it exists, else create it

I need to update a dataset mylib.dt_old using the dataset dt_new, but I want to first check if it actually exists, otherwise I would get an error. In case it does not exist, I just want to create a dataset mylib.dt_old that stores the information contained in dt_new. I tried the following:

if (exist(mylib.dt_old)) 
then do;
  data   mylib.dt_old;
  update mylib.dt_old  dt_new;
  by date var1 var2; 
  run;
end;
else do;
  data mylib.dt_old;  set dt_new;
  run;
end;

However I get the error, when mylib.dt_old does not exist

ERROR: File MYLIB.DT_OLD.DATA does not exist.

and sas goes on actually executing the else statement (creates dt_old copying dt_new).

Instead if dt_old does exist I get 

   if (exist(mylib.dt_old))
   --
   180
   ERROR 180-322: Statement is not valid or it is used out of proper order.

What am I doing wrong? PS: I am a beginner in SAS.

Upvotes: 1

Views: 2055

Answers (1)

Jeff
Jeff

Reputation: 1807

What you're trying to do would actually qualify as macro programming in SAS, which is sometimes considered an "advanced" topic.

The normal if-then control logic you're using is what SAS considers data-step code, i.e. it's only valid in the data step. But there is a "macro" language that looks similar, but is distinguished by % prefixes. Here's how your modified code might look:

%macro updater();
    %if %sysfunc(exist(mylib.dt_old)) 
    %then %do;
        data   mylib.dt_old;
            update mylib.dt_old  dt_new;
            by date var1 var2; 
        run;
    %end;
    %else %do;
        data mylib.dt_old;
            set dt_new;
        run;
    %end;
%mend updater;
%updater()

While this example is sort-of straightforward, the SAS macro language is frequently counterintuitive (to me at least). If you're a beginner it might be a good idea to find and read an "into to SAS macros" online.

Upvotes: 3

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