Question

我只需要返回具有排名的比赛，该排名位于表league_ranking内，每个比赛都与round_id列相关。

基本上，查询应该返回特定国家/地区的所有比赛，但条件是该国家/地区的所有比赛都必须具有排名，所以我这样做了：

SELECT c.name AS competition_name,
  c.id AS competition_id
  FROM competition c
  JOIN competition_seasons s ON s.competition_id = c.id
  JOIN competition_rounds r ON r.season_id = s.id
  LEFT JOIN league_ranking l ON l.round_id = r.id
  WHERE c.country_id = :country_id AND l.round_id IS NULL
  GROUP BY c.id
  ORDER BY c.name ASC

此查询还返回没有排名的竞争，例如：

竞争

id | country_id | name
202     12         Cup

competition_seasons

id  | competition_id | name
955       202           2018/2019

competition_rounds

id    | season_id |
 2122    955

联赛排名

该回合没有记录

上面的查询还将返回竞争202，我做错了什么？

Answer 1

您当前的查询专门用于仅返回排名为 no 的比赛，因为它使用LEFT JOIN至league_ranking，然后检查{{1} }，只有在比赛没有联赛排名时（即没有与l.round_id IS NULL匹配的行），这才是正确的。如果您只想拥有联赛排名的<em> 比赛，请将l.round_id = r.id更改为LEFT JOIN，然后删除JOIN条件。请注意，您不需要l.round_id IS NULL子句，而我已将其删除。

GROUP BY

Demo on dbfiddle

Answer 2

请尝试此查询

SELECT c.name AS competition_name, c.id AS competition_id FROM competition c JOIN competition_seasons s ON s.competition_id = c.id JOIN competition_rounds r ON r.season_id = s.id JOIN league_ranking l ON l.round_id = r.id WHERE c.country_id = :country_id GROUP BY c.id ORDER BY c.name ASC

无法排除未加入的记录

2 个答案: