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Comparison for Sorting (cont)

In reality, need to sort on multiple attributes and ASC/DESC, e.g. 

-- example multi-attribute sort
select * from Students
order by age desc, year_enrolled

Sketch of multi-attribute sorting function 

int tupCompare(r1,r2,criteria)
{
   foreach (f,ord) in criteria {
      if (ord == ASC) {
         if (r1.f < r2.f) return -1;
         if (r1.f > r2.f) return 1;
      }
      else {
         if (r1.f > r2.f) return -1;
         if (r1.f < r2.f) return 1;
      }
   }
   return 0;
}