使用子查询与 LEFT JOIN 一起选择 MAX 值

我有一个获取搜索结果的查询，效果很好。

查询成功示例：

 SELECT
    individuals.individual_id,
    individuals.unique_id,
    TIMESTAMPDIFF(YEAR,individuals.day_of_birth,CURDATE()) AS age,
    individuals_dynamics.id,
    individuals_achievements.degree
  FROM
    individuals as individuals
  LEFT JOIN
    individuals_dynamics AS individuals_dynamics ON individuals.unique_id = individuals_dynamics.individual_id
  LEFT JOIN
    individuals_achievements AS individuals_achievements ON individuals.unique_id = individuals_achievements.individual_id
  WHERE
    $uuid_access_status $display_type $detailed_search_query
  ORDER BY 
    $search_sort $search_order

从现在开始，我的记录就不止一条了individuals_achievements每个人，这是我想获得最大值（最新ID）的地方。

我尝试了许多不同的查询，但总是收到错误对非对象调用成员函数 rowCount()。

我明白这个错误的含义，但我无法弄清楚我在哪里犯了这个错误以及一般情况下出了什么问题。

我的失败尝试的例子：

  SELECT
    individuals.individual_id,
    individuals.unique_id,
    TIMESTAMPDIFF(YEAR,individuals.day_of_birth,CURDATE()) AS age,
    individuals_dynamics.id,
    individuals_achievements.degree
  FROM
    individuals as individuals
  LEFT JOIN
    individuals_dynamics AS individuals_dynamics ON individuals.unique_id = individuals_dynamics.individual_id
  INNER JOIN
  (
       SELECT
            degree, MAX(id) AS latest_record
       FROM
            individuals_achievements
       GROUP BY
            latest_record
  ) individuals_achievements AS individuals_achievements ON individuals.unique_id = individuals_achievements.individual_id
  WHERE
    $uuid_access_status $display_type $detailed_search_query
  ORDER BY 
    $search_sort $search_order

我在这里缺少什么？有什么帮助吗？

这是你的from clause:

  FROM
    individuals as individuals
  LEFT JOIN
    individuals_dynamics AS individuals_dynamics ON individuals.unique_id = individuals_dynamics.individual_id
  INNER JOIN
  (
       SELECT
            degree, MAX(id) AS latest_record
       FROM
            individuals_achievements
       GROUP BY
            latest_record
  ) individuals_achievements AS individuals_achievements ON individuals.unique_id = individuals_achievements.individual_id;

我至少可以发现三个问题。第一个是individuals_achievements AS individuals_achievements;第二个是参考individuals_achievements.individual_id它不在子查询中。第三个是group by latest_record.

  FROM individuals LEFT JOIN
       individuals_dynamics
       ON individuals.unique_id = individuals_dynamics.individual_id LEFT JOIN
       individuals_achievements
       ON individuals.unique_id = individuals_achievements.individual_id JOIN
       (SELECT ia.individual_id, MAX(ia.id) AS latest_record
        FROM individuals_achievements ia
        GROUP BY ia.individual_id
       ) iamax
       ON individuals.unique_id = iamax.individual_id and
          individuals_achievements.id = iamax.latest_record

这会添加一个额外的子查询，其中包含最新记录的 id。

顺便说一下，表别名与表名同名是多余的。这只会让查询变得混乱。此外，最好使用别名的表缩写，例如ia for individuals_achievements。因为这个答案只关注from条款，我没有做出这样的改变。