Question

我有以下表格

1. user
+----+-------------------+
| id | email             |
+----+-------------------+
|  2 | user1@example.com |
|  3 | user2@example.com |
|  1 | user3@example.com |
+----+-------------------+

2. answer
+----+---------+-------------+-----------+---------------------+
| id | user_id | question_id | option_id | created             |
+----+---------+-------------+-----------+---------------------+
|  1 |       2 |           1 |         5 | 2015-12-19 15:15:07 |
|  2 |       2 |           1 |         5 | 2015-12-19 15:16:05 |
|  3 |       2 |           2 |         3 | 2015-12-19 15:16:06 |
|  4 |       2 |           3 |         3 | 2015-12-19 15:16:08 |
|  5 |       2 |           1 |         1 | 2015-12-19 15:32:46 |
|  6 |       2 |           1 |         4 | 2015-12-19 15:39:22 |
|  7 |       2 |           1 |         2 | 2015-12-19 15:39:23 |
|  8 |       2 |           1 |         2 | 2015-12-19 15:40:38 |
|  9 |       2 |           1 |         1 | 2015-12-19 15:41:25 |
+----+---------+-------------+-----------+---------------------+

我想获取option_id，其中大多数事件按用户分组并具有以下条件

如果最多出现两次或更多次option_id，请获取最后一条记录。

参考上面的答案表，如您所见，option_id最多出现四次，在这种情况下，我希望返回列表中的最后一个option_id 1

以下是我用来实现我想要的查询

SELECT
    option_id,
    COUNT(option_id) as occurence
FROM
    answer
GROUP BY
    option_id
ORDER BY 
    occurence DESC LIMIT 1;

这是有效的，但是当我添加WHERE条件时，它给了我option_id 5，而我期望option_id 1

SELECT
    option_id,
    COUNT(option_id) as occurence
FROM
    answer
WHERE
    user_id = 2
GROUP BY
    option_id
ORDER BY 
    occurence DESC LIMIT 1;

我在这里缺少什么？

注意：这是此link的后续问题，我在此重新发布的原因是发布同一问题的简化版本。

Answer 1

我在桌子上做了类似的事情，这是我的解决方案：

SELECT option_id
FROM answer 
WHERE id = (SELECT id
            FROM answer 
            WHERE user_id = 2 
            GROUP BY option_id 
            ORDER BY COUNT(option_id) DESC, id DESC
            LIMIT 1)

或者查看在查询中ORDER BY occurence DESC, id DESC会发生什么。

Answer 2

一步一步：

计算option_id出现次数（按option_id和count分组）
从上面的数字中获取最大数量（最大数量或按订单数量限制1） 3，使用此计数获取所有option_id。
使用其中一个option_ids获取所有记录。
仅保留此查找记录的最后一条记录（按限制1排序）。

查询：

select *
from answer
where option_id in
(
  select option_id
  from answer
  group by option_id
  having count(*) =
  (
    select count(*) as cnt
    from answer
    group by option_id
    order by count(*) desc limit 1
  )
)
order by created desc limit 1;

Answer 3

如果它真的只是您感兴趣的order_id，则只需将MAX(created) DESC添加到您的ORDER BY：

SELECT
    option_id,
    COUNT(option_id) as occurence
FROM
    answer
WHERE
    user_id = 2
GROUP BY
    option_id
ORDER BY 
    occurence DESC, MAX(created) DESC LIMIT 1;

获取表中最大的值

3 个答案: