Sql 我可以在CASE语句中使用可变条件吗？

想象一下一个企业与人之间的互动：

+-----------+---------------------+-----------------+
| user_name | action_timestamp    | action          |
+-----------+---------------------+-----------------+
| john      | 2017-01-01 10:00:00 | phone_call      |
+-----------+---------------------+-----------------+
| john      | 2017-01-02 12:00:00 | became_customer |
+-----------+---------------------+-----------------+
| john      | 2017-01-03 14:00:00 | phone_call      |
+-----------+---------------------+-----------------+
| jane      | 2016-08-06 10:00:00 | phone_call      |
+-----------+---------------------+-----------------+
| jane      | 2016-08-06 11:00:00 | phone_call      |
+-----------+---------------------+-----------------+
| jane      | 2016-08-06 12:00:00 | became_customer |
+-----------+---------------------+-----------------+
| tony      | 2016-12-01 15:00:00 | phone_call      |
+-----------+---------------------+-----------------+

我想做这样的事情：

+-----------+---------------+-------------+---------------------+------------------------------+-----------------------------+
| user_name | total_actions | is_customer | became_customer     | interactions_before_customer | interactions_after_customer |
+-----------+---------------+-------------+---------------------+------------------------------+-----------------------------+
| john      | 3             | TRUE        | 2017-01-02 12:00:00 | 1                            | 1                           |
+-----------+---------------+-------------+---------------------+------------------------------+-----------------------------+
| jane      | 3             | TRUE        | 2016-08-06 12:00:00 | 2                            | 0                           |
+-----------+---------------+-------------+---------------------+------------------------------+-----------------------------+
| tony      | 1             | FALSE       | NULL                | 1                            | 0                           |
+-----------+---------------+-------------+---------------------+------------------------------+-----------------------------+

前4列对于一些分组和案例来说是微不足道的，但我不知道如何在客户之前和客户之后进行第5列和第6列交互，因为案例是基于前一列的结果预测的，并且需要在行之间变化

---

这比表面上看起来简单吗？如果有人关心我不在呼叫中心工作，这只是一个简单得多的类比，我正在尝试做什么

这会给你一个想法。我已经在ORACLE上进行了测试，它运行良好

WITH CUS_DET AS (
    SELECT *
    FROM INTERACTIONS
    WHERE ACTION = 'became_customer'
)
SELECT INTERACTIONS.USER_NAME
  , SUM(CASE 
    WHEN (CUS_DET.ACTION_TIMESTAMP IS NULL
            OR INTERACTIONS.ACTION_TIMESTAMP < CUS_DET.ACTION_TIMESTAMP)
    THEN 1 
    ELSE 0 
  END) BEF
  , SUM(CASE 
    WHEN INTERACTIONS.ACTION_TIMESTAMP > CUS_DET.ACTION_TIMESTAMP 
    THEN 1 
    ELSE 0 
  END) AFT
FROM INTERACTIONS
  LEFT OUTER JOIN CUS_DET
    ON INTERACTIONS.USER_NAME = CUS_DET.USER_NAME
GROUP BY INTERACTIONS.USER_NAME;

---

这会给你一个想法。我已经在ORACLE上进行了测试，它运行良好

WITH CUS_DET AS (
    SELECT *
    FROM INTERACTIONS
    WHERE ACTION = 'became_customer'
)
SELECT INTERACTIONS.USER_NAME
  , SUM(CASE 
    WHEN (CUS_DET.ACTION_TIMESTAMP IS NULL
            OR INTERACTIONS.ACTION_TIMESTAMP < CUS_DET.ACTION_TIMESTAMP)
    THEN 1 
    ELSE 0 
  END) BEF
  , SUM(CASE 
    WHEN INTERACTIONS.ACTION_TIMESTAMP > CUS_DET.ACTION_TIMESTAMP 
    THEN 1 
    ELSE 0 
  END) AFT
FROM INTERACTIONS
  LEFT OUTER JOIN CUS_DET
    ON INTERACTIONS.USER_NAME = CUS_DET.USER_NAME
GROUP BY INTERACTIONS.USER_NAME;

---

如果用户只能成为客户一次，则使用条件聚合：

select 
    t.user_name
  , case when c.action_timestamp is not null then 'Yes' else 'No' end as Is_Customer
  , c.action_timestamp as became_customer
  , count(case when t.action_timestamp < coalesce(c.action_timestamp,'2525-01-01') then 1 end) as interactions_before_customer 
  , count(case when t.action_timestamp > c.action_timestamp then 1 end) as interactions_after_customer 
from t
  left join t as c
    on t.user_name = c.user_name
      and c.action = 'became_customer'
group by t.user_name, c.action_timestamp

---

如果用户只能成为客户一次，则使用条件聚合：

select 
    t.user_name
  , case when c.action_timestamp is not null then 'Yes' else 'No' end as Is_Customer
  , c.action_timestamp as became_customer
  , count(case when t.action_timestamp < coalesce(c.action_timestamp,'2525-01-01') then 1 end) as interactions_before_customer 
  , count(case when t.action_timestamp > c.action_timestamp then 1 end) as interactions_after_customer 
from t
  left join t as c
    on t.user_name = c.user_name
      and c.action = 'became_customer'
group by t.user_name, c.action_timestamp

---

啊，很抱歉，很难在这些答案中做出选择！我之所以选择这一款，是因为你是SQL名人，我也了解了coalesce，但Pons也很管用，他提前了几分钟就到了。谢谢你的回复：啊，很抱歉，很难在这些答案中做出选择！我之所以选择这一款，是因为你是SQL名人，我也了解了coalesce，但Pons也很管用，他提前了几分钟就到了。谢谢你的回复：太棒了。谢谢令人惊叹的谢谢