MySQL 8.0

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drop table if exists prlines;

create table if not exists prlines (id int, prev_id int);

insert into prlines values (1, NULL), (2, NULL), (3, 1), (4, 2), (5, 3), (6, 5), (7, 6);

Records: 7  Duplicates: 0  Warnings: 0

with recursive cte(p, c, f) as (

select p.*, p.prev_id = 5 from prlines p where p.id = 5 or p.prev_id = 5

union all

select p.*, c.f from cte c join prlines p on case when c.f then p.prev_id = c.p else p.id = c.c end

)

select case when f then p else c end prev_id from cte where c is not null order by f;