CREATE OR REPLACE TYPE NumberList IS TABLE OF number(5); 

DROP TABLE test

CREATE TABLE test ( 
     id_std int 
     , marks NumberList ) 
Nested table marks store as numere_necesare

insert into test(id_std, marks ) 
values (1,NumberList(6,7,8))

update test 
set marks = marks multiset union all numberlist(42) 
where id_std = 1 

select id_std 
       , t2.column_value as mark 
from test t1 
     , table(t1.marks) t2 

 update test 
 set marks = marks multiset union all numberlist(23, 69) 
 where id_std = 1 

select id_std 
       , t2.column_value as mark 
from test t1 
     , table(t1.marks) t2