Question

我正在尝试返回与已加入记录关联的GROUP_CONCAT 5个匹配项，我尝试按以下方式设置查询：

$sql = $this->db->prepare("SELECT l.*,
t.name as team_name,
r.name AS rank_name,
r.color AS rank_color,
GROUP_CONCAT(DISTINCT m.* LIMIT 5, ORDER BY m.id) AS last_five_matches,
FROM league_ranking l
LEFT JOIN team t ON l.team_id = t.id
LEFT JOIN competition_ranks r ON l.rank = r.id
LEFT JOIN `match` m ON m.home_team_id = l.team_id OR m.away_team_id = l.team_id
WHERE l.round_id = :round_id AND m.status = 5");

你可以看到我想要返回状态= 5的5场比赛。

我得到的问题是：

SQLSTATE [42000]：语法错误或访问冲突：1064 SQL语法中有错误;检查与MySQL服务器版本对应的手册，以便在'* LIMIT 5，ORDER BY m.id）附近使用正确的语法AS last_five_matches，来自league_ranking l

我不明白GROUP_CONCAT上的问题出在哪里，请注意，如果我删除GROUP_CONCAT查询有效，是否有任何帮助？

更新

这是编辑的查询：

"SELECT l.*,
t.name as team_name,
r.name AS rank_name,
r.color AS rank_color,
GROUP_CONCAT(DISTINCT m.id ORDER BY m.id) AS last_five_matches
FROM league_ranking l
LEFT JOIN team t ON l.team_id = t.id
LEFT JOIN competition_ranks r ON l.rank = r.id
LEFT JOIN `match` m ON m.home_team_id = l.team_id OR m.away_team_id = l.team_id
WHERE l.round_id = :round_id AND m.status = 5
GROUP BY team_name"

我得到了：

语法错误或访问冲突：1055 SELECT列表的表达式＃1不在GROUP BY子句中，并且包含非聚合列'swp.l.position'，它在功能上不依赖于GROUP BY子句中的列;这与sql_mode = only_full_group_by
不兼容

Answer 1

根据the mysql documentation，您无法将LIMIT语句与GROUP_CONCAT()一起使用。试试这个：

.. GROUP_CONCAT(DISTINCT m.id, ORDER BY m.id) AS last_five_matches ..

Answer 2

GROUP_CONTACT是Aggregation Operation，你需要有一个GROUP BY子句描述你在哪些值下聚合记录

SELECT l.*,
   t.name as team_name,
   r.name AS rank_name,
   r.color AS rank_color,
   GROUP_CONCAT(DISTINCT m.<column_name> LIMIT 5, ORDER BY m.id) AS last_five_matches,
FROM league_ranking l
   LEFT JOIN team t ON l.team_id = t.id
   LEFT JOIN competition_ranks r ON l.rank = r.id
   LEFT JOIN `match` m ON m.home_team_id = l.team_id OR m.away_team_id = l.team_id
WHERE l.round_id = :round_id AND m.status = 5
GROUP BY team_name, rank_name, rank_color

Answer 3

我相信你想要：

SELECT t.name as team_name, r.name AS rank_name, r.color AS rank_color,
       SUBSTRING_INDEX(GROUP_CONCAT(DISTINCT m.id ORDER BY m.id), ',', 5) AS last_five_matches
FROM team t LEFT JOIN
     league_ranking l
     ON l.team_id = t.id LEFT JOIN
     competition_ranks r
     ON l.rank = r.id LEFT JOIN
     `match` m
     ON m.home_team_id = l.team_id OR m.away_team_id = l.team_id
WHERE l.round_id = :round_id AND m.status = 5
GROUP BY t.name, r.name, r.color;

注意：

GROUP BY个密钥与SELECT中的未聚合列完全匹配。
我删除了l.*。它在GROUP BY查询中没有意义。
GROUP_CONCAT()不支持LIMIT。听起来不错，但它并不存在。相反，形成列表然后采取前5个元素。
我将JOIN订单更改为以team开头。您似乎希望每个团队占一行，因此应该是FROM。

无法执行GROUP_CONCAT

3 个答案: