Mysql 如何选择另一个表中没有链接记录为空的记录？

我有以下SQL：

SELECT tournaments_blg.tournament_id_blg
FROM matches_blg  LEFT JOIN tournaments_blg ON tournaments_blg.tournament_id_blg = matches_blg.tournament_id_blg
WHERE matches_blg.match_id_op IS NULL
GROUP BY tournaments_blg.tournament_id_blg

这将选择所有比赛\u blg.touring\u id\u blg，其中任何一个比赛\u blg.match\u id\u op为空

如果所有比赛\u blg.match\u id\u op均为空，我如何仅选择所有比赛\u blg.touring\u id\u blg

或

试试这个：

---

从比赛中选择锦标赛\u blg.Tournams\u id\u blg，其中比赛\u blg.match\u id\u op不在比赛中选择锦标赛\u blg

SELECT tb.tournament_id_blg
FROM tournaments_blg tb
LEFT JOIN matches_blg mb ON tb.tournament_id_blg = mb.tournament_id_blg 
                        AND mb.match_id_op IS NOT NULL
WHERE mb.tournament_id_blg IS NULL

SELECT tb.tournament_id_blg
FROM tournaments_blg tb
WHERE NOT EXISTS ( SELECT NULL
                   FROM matches_blg mb 
                   WHERE tb.tournament_id_blg = mb.tournament_id_blg 
                     AND mb.match_id_op IS NOT NULL )