How to display two lines in one?

Question

MySQL

There is (for example) a table matches and match_opponents.
Match_opponents has match_id and opponent_id (for each match there are two opponents, i.e. for match = 123 there will be two lines with match id and opponent id).

Select * 
from matches m
inner join match_opponents op on op.match_id = m.match_id
where m.status like "started";

This outputs two lines for each match, and I need one match in one line
like this:
match_id | opponent1 | opponent2

Answer 1

Use grouping

select
  m.match_id,
  min(opponent_id) as op1, max(opponent_id) as op2
from match_opponents op
inner join matches m on op.match_id = m.match_id
where m.status = "started"
group by m.match_id;

SQL fiddfe

Answer 2

distinct + concat, though there will be only 2 fields