您可以将teams表与其自身交叉联接，以生成所有可能的匹配组合，然后排除那些已经使用not exists发生的匹配组合：
如果您同时需要team 1/team 2和team 2/team 1游戏，则：

select t1.id_team id_team1, t2.id_team id_team2
from teams t1
inner join teams t2 on t1.id_team != t2.id_team
where not exists (
    select 1 from matches m where m.id_team1 = t1.id_team and m.id_team2 = t2.id_team2
)

如果您希望每对球队之间只进行一场比赛，那么我们需要添加一些条件逻辑：

select t1.id_team id_team1, t2.id_team id_team2
from teams t1
inner join teams t2 on t1.id_team < t2.id_team
where not exists (
    select 1 
    from matches m 
    where t1.id_team = least(m.id_team1, m.id_team2)
      and t2.id_team = greatest(m.id_team1, m.id_team2)
)