select m.ID,
       m.PROJECT_ID,
       m.NAME,
       m.DESCRIPTION,
       m.DUE_DATE,
       m.CREATED,
       m.CREATED_BY,
       m.UPDATED,
       m.UPDATED_BY,
       case when sysdate >= p.completed_date then null
         else 'UD'
       end operation
from SAMPLE$PROJECT_MILESTONES m
,    sample$projects p
where m.project_id = p.id