libname x <... relational-dbms ...> 

   proc sql;                                                                   
      create table temp as                                                     
         select distinct table0.comax as comax label='comax',                  
                table1.coetb as coetb label='coetb',                           
                max(table2.ddenv) as ddenv label='max ddenv' format=yymmddd10. 
         from  x.custid table0                                                 
               join x.tr1c_crm table1 on table0.comax = table1.comax             
               join x.tj3f_crm table2 on  table0.comax = table2.comax            
                                   and table1.coetb = table2.coetb;            
   quit;