MySQL 8.0

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.
create table cars (id int);
create table car_tags (car_id int, tag_id int);
insert into cars 
  values (297360),(564800),(564830),(1720948),(123456),(234567),(345678);

Records: 7  Duplicates: 0  Warnings: 0


insert into car_tags 
  values (297360,5),(564800,3),(564800,4),(564830,2),(345678,4),
         (1720948,1),(123456,3),(123456,4),(123456,6),(234567,3);

Records: 10  Duplicates: 0  Warnings: 0


SELECT 
  c.id, 
  GROUP_CONCAT(DISTINCT t.tag_id ORDER BY t.tag_id) AS tag_ids 
FROM 
cars c INNER JOIN car_tags t
ON c.id = t.car_id
GROUP BY c.id
ORDER BY c.id


id
tag_ids


123456
3,4,6

234567
3

297360
5

345678
4

564800
3,4

564830
2

1720948
1


SELECT 
  c.id, 
  GROUP_CONCAT(DISTINCT t.tag_id ORDER BY t.tag_id) AS tag_ids 
FROM 
cars c INNER JOIN car_tags t
ON c.id = t.car_id
GROUP BY c.id
HAVING 
  SUM(t.tag_id = 3) > 0 
  AND SUM(t.tag_id = 4) > 0
ORDER BY c.id


id
tag_ids


123456
3,4,6

564800
3,4


SELECT 
  c.id, 
  GROUP_CONCAT(DISTINCT t.tag_id ORDER BY t.tag_id) AS tag_ids 
FROM 
cars c INNER JOIN car_tags t
ON c.id = t.car_id
WHERE t.tag_id IN (3,4)
GROUP BY c.id
HAVING 
  SUM(t.tag_id = 3) > 0 
  AND SUM(t.tag_id = 4) > 0
ORDER BY c.id


id
tag_ids


123456
3,4

564800
3,4


SELECT 
  c.id, 
  GROUP_CONCAT(DISTINCT t.tag_id ORDER BY t.tag_id) AS tag_ids 
FROM 
cars c INNER JOIN car_tags t
ON c.id = t.car_id
WHERE t.tag_id IN (3,4)
GROUP BY c.id
ORDER BY c.id


id
tag_ids


123456
3,4

234567
3

345678
4

564800
3,4