SQL 計算跳出率

Question

我有以下 SQL 表（Postgres）：

+-----------+------------+-------+
| SessionID |  Received  | Event |
+-----------+------------+-------+
|         1 | 1595207019 | visit |
|         1 | 1595207020 | play  |
|         2 | 1595207040 | visit |
|         1 | 1595207050 | click |
+-----------+------------+-------+

我想計算跳出率，其中跳出被定義為訪問事件，之后沒有任何其他具有相同 session id 的事件。

Answer 1

嗯。 . . 我認為您想通過session_id進行總結並計算訪問類型。 然后聚合。 您的問題不是 100% 清楚，但我認為：

select (count(*) filter (where num_notvisits = 0) * 1.0 / count(*)) as bounce_rate
from (select session_id,
             count(*) filter (where event = 'visit') as num_visits,
             count(*) filter (where event <> 'visit') as num_notvisits
      from t
      group by session_id
     ) s
where num_visits > 0;

這是訪問和非訪問事件的會話數除以訪問的會話數的比率。

實際上，您可以更簡單地將外部 select 表述為：

select avg( (num_notvisits = 0)::int ) as bounce_rate

Answer 2

您可以像這樣顯式查詢“反彈”的數量：

select count(*)
from t as t1
where t1.event = 'visit'
  and not exists (select * from t as t2 where t1.received < t2.received and t1.sessionid = t2.sessionid)

不確定“跳出率”的分母具體是什么？ 每個 session 的反彈？ # 反彈/# 事件？