COMMENT ON
  { COLUMN [ schema. ]
    { table. | view. | materialized_view. } column
  | EDITION edition_name
  | INDEXTYPE [ schema. ] indextype
  | MATERIALIZED VIEW materialized_view
  | MINING MODEL [ schema. ] model
  | OPERATOR [ schema. ] operator
  | TABLE [ schema. ] { table | view }
  }
  IS string ;