How to make a macro resolve to "0" when there's not value

[HitmonTran]

Hi,

My macro is not resolving because there is no data for that variable. I tried using data _null_ and set it as "0" values when data does not exist, but no luck. How do I set it to "0" in this situation?

 
proc sql;
select count(*) into :obs from g3pop;
quit;
%put obs: &obs.;

%if &obs > 0 %then %do;  
	proc sql noprint;
	
        *Number/percent of subjects experiencing the events - Toxicity>=3 event;
        select (strip(put(count (distinct usubjid), best.))) into :ng3a1 from g3pop where (trtn=1);            
        select (strip(put(&ng3a1./&trt1.*100, 2.))) into :pg3a1 from g3pop where (trtn=1); 
        select strip(put(&ng3a1., 5.))||' ('||strip(put(&pg3a1., 2.))||'%)' into :a2 from g3pop where (trtn=1);
        
        select (strip(put(count (distinct usubjid), best.))) into :ng3p2 from g3pop where (trtn=2);            
        select (strip(put(&ng3p2./&trt2.*100, 2.))) into :pg3p2 from g3pop where (trtn=2); 
        select strip(put(&ng3p2., 5.))||' ('||strip(put(&pg3p2., 2.))||'%)' into :p2 from g3pop where (trtn=2);
    quit;
%end; 

%else %do;
	data _null_;
		call symput('p2','0 (0%)');
		call symput('t2','0 (0%)');
		call symput('a2','0 (0%)');
	run;
%end;

[jimbarbour · Accepted solution]

Put this code before your Proc Report:

%GLOBAL p2;
%IF %BQUOTE(&p2) = %BQUOTE() %THEN
    DO;
        %LET p2 = 0;
    END;

Jim

P.S.  The second %BQUOTE isn't, strictly speaking, necessary, but I like it just for code readability.  Note that there is NOT a space between the parentheses in the second %BQUOTE.

[ChrisNZ]

The simplest way would be to add

%let p2=0 (0%);
%let t2=0 (0%);
%let a2=0 (0%);

before the proc sql. Then the value gets overwritten if available.