Oracle 11g Release 2

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.

CREATE TABLE Restaurants (restaurant_ID Integer, name VARCHAR2(10));
 
INSERT INTO Restaurants (restaurant_ID, name)
  select '1', 'Macdonalds' from dual
  union all 
  select '2', 'Hubert' from dual
  union all
  select '3', 'Dorsia' from dual
  union all
  select '4', 'Another' from dual;
 
4 rows affected

CREATE TABLE Identifier (restaurant_ID INTEGER, food_ID INTEGER);

INSERT INTO Identifier (restaurant_ID, food_ID) 
  select '1', '1' from dual 
  union all
  select '1', '4' from dual
  union all
  select '2', '1' from dual 
  union 
  select '2', '7' from dual
  union 
  select '2', '8' from dual
  union
  select '3', '1' from dual 
  union 
  select '3', '4' from dual
  union
  select '4', '1' from dual 
  union 
  select '4', '7' from dual
  union
  select '4', '8' from dual;

 
10 rows affected

CREATE TABLE Food (food_ID INTEGER, food_name VARCHAR2(7));
INSERT INTO Food (food_ID, food_name)
  select '1', 'Chips' from dual
  union 
  select '2', 'Burgers' from dual
  union 
  select '3', 'Salmon' from dual;
3 rows affected

With cte as
(select t1.restaurant_id, listagg(food_id,',') within group (order by restaurant_id, food_id) as food_list
from
  Identifier t1
  group by t1.restaurant_id)
select 
   (r1.name||','||r2.name) as restaurants,
   t1.restaurant_id as restaurant_id1,
   r1.name as restaurant_1,
   t2.restaurant_id as restaurant_id2,
   r2.name as restaurant_2,
   t1.food_list as common_food_ids
from cte t1
join cte t2
on t1.restaurant_id < t2.restaurant_id
and t1.food_list = t2.food_list
left join Restaurants r1
on t1.restaurant_id = r1.restaurant_id
left join Restaurants r2
on t2.restaurant_id = r2.restaurant_id; 


RESTAURANTS
RESTAURANT_ID1
RESTAURANT_1
RESTAURANT_ID2
RESTAURANT_2
COMMON_FOOD_IDS


Macdonalds,Dorsia
1
Macdonalds
3
Dorsia
1,4

Hubert,Another
2
Hubert
4
Another
1,7,8

RESTAURANTS	RESTAURANT_ID1	RESTAURANT_1	RESTAURANT_ID2	RESTAURANT_2	COMMON_FOOD_IDS
Macdonalds,Dorsia	1	Macdonalds	3	Dorsia	1,4
Hubert,Another	2	Hubert	4	Another	1,7,8