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我在构建查询以执行以下操作时遇到问题：

按 activity_type_id 过滤联系人，仅显示最近活动具有所需 activity_type_id 或为 NULL（无活动）的联系人

表格的结构如下：

一个联系人可以有许多不同类型的活动

activity:
id
contact_id
activity_type_id
date

contact:
id
first_name
last_name

到目前为止我有这个：

SELECT * FROM (
    SELECT c.first_name, c.last_name, a.activity_type_id, MAX(a.date) AS maxdate 
    FROM contact AS c
    LEFT JOIN activity AS a ON a.contact_id = c.id
    GROUP BY c.id
    ORDER BY c.first_name  ASC
) AS act

然后将其添加到过滤器：

WHERE activity_type_id = 3 /* <- I would like to filter using this */

但是，对于具有多个活动的联系人，我得到了错误的 activity_type_id。

我最终想将其用作 Doctrine 1.2 查询，但我希望首先在 MySQL 中工作。

谢谢你。

最终的解决方案

SELECT c.first_name, c.last_name, a.activity_type_id FROM contact c
  LEFT JOIN
    (SELECT a1.contact_id, a1.date, a1.activity_type_id FROM activity a1
      JOIN (SELECT contact_id, MAX(DATE) DATE FROM activity GROUP BY contact_id) a2
        ON a1.contact_id = a2.contact_id AND a1.date = a2.date
     ) a
  ON c.id = a.contact_id  
WHERE a.activity_type_id = 2;

最后的 where 原因可以调整为返回各种活动类型或设置为 IS NULL。

DQL 1.2 兼容版本

SELECT * FROM contact c
LEFT JOIN activity ON c.id = contact_id
WHERE ROW (c.id,DATE) IN (SELECT contact_id, MAX(date) date FROM activity  GROUP BY contact_id)
AND activity_type_id = 2
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1 回答 1

1

试试这个查询 -

编辑：添加了 a1.activity_type_id

SELECT c.first_name, c.last_name FROM contacts c
  LEFT JOIN
    (SELECT a1.contact_id, a1.date, a1.activity_type_id FROM activity a1
      JOIN (SELECT contact_id, MAX(date) date FROM activity GROUP BY contact_id) a2
        ON a1.contact_id = a2.contact_id AND a1.date = a2.date
     ) a
  ON c.contact_id = a.contact_id
WHERE a.contact_id IS NULL OR a.activity_type_id = 3;
于 2012-08-07T06:53:37.790 回答