Sas macro conditional join using %if %then %else

Question

I am trying to join two tables, weight 1 and weight2. I want to join these two tables on ID1=ID2 first. if there is a missing ID, I will join on DOB1=DOB2. I want the program to compare each row in the table. but sas saw the first ID is missing in weight2 table, then it completely switch to the else statement, and use DOB1=DOB2 to join.

My Ideal result is to have four rows joined. but now sas only gives me three rows.

data weight1;    

   input ID1 $ Week1 DOB1; 

   datalines;            
1111 195  101
2222 220  102
3333 173  103
4444 135  104
;                           

proc print data=weight1;    
run; 

data weight2;    
  infile datalines missover;  
   input ID2 $ Week2 DOB2; 

   datalines;            
     195  101
2222 220  102
3333 173  103
4444 135  104
;                           

proc print data=weight2;    
run;  

options mlogic symbolgen mprint; 
%macro test ;
proc sql;
create table final as 
select a.ID1, a.DOB1, b.ID2,b.DOB2

from weight1 a
%if %sysfunc(exist(b.ID2)) %then 
inner join weight2 b 
on a.ID1 = b.ID2;
%else 
/*%if %sysfunc(not exist(b.IDnumber))*/
inner join weight2 b
on a.DOB1 = b.DOB2
;
;
quit;
%mend test;

%test

Sas log:

LOGIC(TEST):  Beginning execution.
MPRINT(TEST):   proc sql;
MLOGIC(TEST):  %IF condition %sysfunc(exist(b.ID2)) is FALSE
MPRINT(TEST):   create table final as select a.ID1, a.DOB1, b.ID2,b.DOB2 from weight1 a inner join weight2 b on a.DOB1 = b.DOB2 ;
NOTE: Table WORK.FINAL created, with 3 rows and 4 columns.

this is my ideal result

ID1    DOB1 ID2    DOB2
1111    101         101
2222    102 2222    102
3333    103 3333    103
4444    104 4444    104

Answer 1

A case expression can be used as join criteria.

Do not use macro. Your use of %sysfunc(exist is just wrong, the exist function checks for the existence of a data set, and %sysfunc is performed pre source code compilation time, not at SQL execution time.

Use a case expression to evaluate the pre-conditions for your equality check.

Example:

data weight1;    

   input ID1 $ Week1 DOB1; 

   datalines;            
1111 195  101
2222 220  102
3333 173  103
4444 135  104
;                           

data weight2;    
  infile datalines missover;  
   input ID2 $ Week2 DOB2; 

   datalines;            
.    195  101
2222 220  102
3333 173  103
4444 135  104
;                           

proc sql;
  create table want as
  select a.ID1, a.DOB1, b.ID2,b.DOB2
  from weight1 a
  join weight2 b
    on case 
         when (a.id1 is not missing and b.id2 is not missing) then a.id1=b.id2
         when (a.dob1 is not missing and b.dob2 is not missing) then a.dob1=b.dob2
         else 0
       end
  ;

NOTE: The case of real data where you have more than one row in each table with missing id and the same date of birth will cause a multiplicative row count effect in the result table. Such as this sample data:

1111 195  101
2222 220  102
3333 173  103
4444 135  104
.    145  105 ***
.    175  105 ***     

and

.    195  101
2222 220  102
3333 173  103
4444 135  104
.    155  105 ***
.    166  105 ***

4 = 2 x 2 result rows from the starred data.