MySQL 5.6

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CREATE TABLE user (
  `id` INTEGER,
  `name` VARCHAR(4),
  `level` INTEGER
);

INSERT INTO user
  (`id`, `name`, `level`)
VALUES
  ('10', 'John', '1'),
  ('11', 'Josh', '2'),
  ('12', 'Mary', '3');

CREATE TABLE level_interaction (
  `level` INTEGER,
  `interact_with` INTEGER
);

INSERT INTO level_interaction
  (`level`, `interact_with`)
VALUES
  ('1', '1'),
  ('1', '2'),
  ('2', '1'),
  ('2', '2'),
  ('2', '3'),
  ('3', '2'),
  ('3', '3');

CREATE TABLE room (
  `room_id` INTEGER,
  `user_id` INTEGER
);

INSERT INTO room
  (`room_id`, `user_id`)
VALUES
  ('1', '10'),
  ('1', '11'),
  ('2', '11'),
  ('2', '12'),
  ('3', '11');
select li.interact_with
from room r
inner join user u on u.id = r.user_id
inner join level_interaction li on li.level = u.level
where r.room_id = 1
group by li.interact_with
having count(*) = (select count(user_id) from room where room_id = 1);


interact_with


1

2


select li.interact_with
from room r
inner join user u on u.id = r.user_id
inner join level_interaction li on li.level = u.level
where r.room_id = 2
group by li.interact_with
having count(*) = (select count(user_id) from room where room_id = 2);


interact_with


2

3


select li.interact_with
from room r
inner join user u on u.id = r.user_id
inner join level_interaction li on li.level = u.level
where r.room_id = 3
group by li.interact_with
having count(*) = (select count(user_id) from room where room_id = 3);


interact_with


1

2

3