MySQL 8.0

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create table tags (
    id int,
    tag varchar(255)
);

insert into tags (id, tag) values
(12, "car|plane|truck"), (11, "plane");
select *
from tags


id
tag


12
car|plane|truck

11
plane


with recursive cte as (
      select id, concat(tag, '|') as rest, cast(null as char(255)) as tag, 1 as lev
      from tags
      union all
      select id, substr(rest, instr(rest, '|') + 1),
             substring_index(rest, '|', 1), lev + 1
      from cte
      where rest <> ''
     )
select id, tag
from cte
where lev > 1


id
tag


12
car

11
plane

12
plane

12
truck