zOs/SQL/ROWNUM

select row_number() over ()
    from sysibm.sysColumns
    fetch first 5 rows only
;
select (row_number () over()) + mm
     , strip(left(name, 40))
     from sysibm.sysColumns,
       (select max(key)+1 mm from A540769.tPer10) m
      fetch first 10 rows only