Oracle SQL: using the LAG analytic clause to show values only when they change

SELECT
   case when nvl(
      LAG( COLUMN_NAME ) over (order by  COLUMN_NAME, further, sorting, columns ),
      'n/a'
   ) <> COLUMN_NAME then
        COLUMN_NAME
   end                       COLUMN_NAME_
   …
FROM
   …
ORDER BY
   COLUMN_NAME,
   further,
   sorting,
   columns