merge 
 into unitofmeasure_user
using dual
  on (
      unitofmeasureid = :unitOfMeasureId AND 
      userid = :userId
     )
when matched 
then update 
        set active = 1
when not matched
then insert (unitofmeasureid, userid) 
       values (:unitOfMeasureId, :userId);

이 쿼리를 보니 참 재밌다.

공부좀 해야겠다. 

stackoverflow.com

-Nicholas Krasnov