MERGE SUBPARTITIONS subpartition_or_key_value
   { , subpartition_or_key_value [, subpartition_or_key_value ]...
   | TO subpartition_or_key_value }
   [ INTO { range_subpartition_desc 
          | list_subpartition_desc
          }
   ]
   [ dependent_tables_clause ]
   [ update_index_clauses ]
   [ parallel_clause ]