create table mydata 
(country varchar2(100));

insert into mydata values ('japan,china,russia,italy');

commit;

SQL> with
  2    input as (select '&input' input from dual),
  3    in_split as (
  4      select distinct regexp_substr(input,'[^,]+',1,level) input
  5      from input
  6      connect by level <= regexp_count(input,',')+1
  7    ),
  8    in_count as (select count(*) in_nb from in_split),
  9    data_split as (
 10      select distinct country, regexp_substr(country,'[^,]+',1,column_value) co
 11      from mydata,
 12           table(cast(multiset(select level from dual
 13                               connect by level <= regexp_count(country,',')+1)
 14                      as sys.odcivarchar2list))
 15    )
 16  select country
 17  from data_split, in_split
 18  where co = input
 19  group by country
 20  having count(*) = (select in_nb from in_count)
 21  /
Enter value for input: japan,russia
COUNTRY
------------------------------------------------------------------------------------
japan,china,russia,italy

1 row selected.

SQL> /
Enter value for input: italy,japan
COUNTRY
-----------------------------------
japan,china,russia,italy

1 row selected.

SQL> /
Enter value for input: france,china

no rows selected

SCOTT@orcl> create table mydata (country varchar2(100));

Table created.

SCOTT@orcl> insert all
  2  into mydata values ('japan,china,russia,italy')
  3  into mydata values ('russia,china,japan,italy')
  4  into mydata values ('russia,china,italy')
  5  into mydata values ('china,japan,italy')
  6  select * from dual;

4 rows created.

SCOTT@orcl> create index myindex on mydata (country) indextype is ctxsys.context parameters ('sync (on commit)');

Index created.

SCOTT@orcl> select * from mydata where contains (country, replace ('japan,russia', ',', ' and ')) > 0;

COUNTRY
--------------------------------------------------------------------------------
japan,china,russia,italy
russia,china,japan,italy

2 rows selected.

CREATE OR REPLACE FORCE VIEW Mydata_v
(
   Country,
   Id_num
)
AS
   SELECT EXTRACT (VALUE (D), '//row/text()').Getstringval () AS Country,
          Id_num
     FROM (SELECT Id_num,
                  Xmltype (
                        '<rows><row>'
                     || REPLACE (Country, ',', '</row><row>')
                     || '</row></rows>')
                     AS Xmlval
             FROM Mydata) X,
          TABLE (XMLSEQUENCE (EXTRACT (X.Xmlval, '/rows/row'))) D;

>desc mydata
 Name                                      Null?    Type
 ----------------------------------------- -------- -------------------
 COUNTRY                                            VARCHAR2(100)
 ID_NUM                                             NUMBER

>desc mydata_v
 Name                                      Null?    Type
 ----------------------------------------- -------- -------------------
 COUNTRY                                            VARCHAR2(4000)
 ID_NUM                                             NUMBER

select id_num
from mydata_v
where country in ('japan','russia')
group by id_num
having count(*) = 2;

    ID_NUM
----------
         1
         2

> select * from mydata;
raydw@rayora1>/

COUNTRY                                      ID_NUM
---------------------------------------- ----------
japan,china,russia,italy                          1
russia,china,japan,italy                          2
russia,china,italy                                3
china,japan,italy                                 4