尝试查找总的唯一出现次数列以及 return 该列中的最大值

Question

我正在尝试查找每个用户会话中 "message to user" 事件的发生次数以及 return 每个用户的最大会话数。所以这意味着我想跟踪有多少用户会话有事件 "message to user"，但如果有意义的话，我想消除在同一会话中发生的重复项？

我也在寻找所有用户的总用户会话

我试图找到这些值但没有成功。我的 table 看起来像这样：

user_id | event                      | user_session_id

1       | message to user            | 1
1       | message to user            | 1
1       | message from user          | 1
1       | message to user            | 1
1       | message from user          | 2 
1       | message to user            | 2  
1       | message to user            | 3
2       | message to user            | 1
2       | message to user            | 1
2       | message from user          | 1
2       | message to user            | 1
2       | message from user          | 2 
2       | message to user            | 2

我的预期输出是这样的：

user_id | event                      | user_session_id | max_session_by_user | total_sessions 
1       | message to user            | 1               | 3                   | 5
1       | message to user            | 2               | 3                   | 5
1       | message to user            | 3               | 3                   | 5
2       | message to user            | 1               | 2                   | 5
2       | message to user            | 2               | 2                   | 5

谢谢

编辑：我在寻找事件列时添加了更多关于我的意思的说明

Answer 1

我不确定 event 列的来源。但你似乎想要：

select user, user_session_id,
       count(*) over (partition by user) as max_sessions
from t
group by user, user_session_id;

Answer 2

首先过滤所需的事件并消除重复项。

然后使用 window 函数添加计数。

SELECT user_id, event, user_session_id,
       count(*) OVER (PARTITION BY user_id) AS max_session_by_user,
       count(*) OVER () AS total_sessions
FROM (SELECT DISTINCT user_id, event, user_session_id
      FROM events_table
      WHERE event = 'message to user') AS q;

尝试查找总的唯一出现次数列以及 return 该列中的最大值

Attempt to find total unique occurrences column as well as return the max value in that column

sql

postgresql

postgresql-9.6