如何在不使用相关子查询的情况下有条件地计算另一个 table 中的行？

Question

我有一个数据集，我必须有条件地计算 table B 中 table A 中两个日期之间的行。我必须在不使用的情况下执行此操作SELECT 子句中的相关子查询，因为这在 Netezza 中不受支持 - 文档：https://www.ibm.com/support/knowledgecenter/en/SSULQD_7.0.3/com.ibm.nz.dbu.doc/c_dbuser_correlated_subqueries_ntz_sql.html.

背景 tables：用户可以登录网站（登录）。当他们登录时，他们可以执行 (actions_taken) 中的操作。 所需的输出是 actions_taken action_date 和 lag_action_date.

之间的行数

在此处找到数据和尝试：http://rextester.com/NLDH13254

Table：actions_taken（添加了计算 - 参见 RexTester。）

| user_id | action_type   | action_date | lag_action_date | elapsed_days |
|---------|---------------|-------------|-----------------|--------------|
| 12345   | action_type_1 | 6/27/2017   | 3/3/2017        | 116          |
| 12345   | action_type_1 | 3/3/2017    | 2/28/2017       | 3            |
| 12345   | action_type_1 | 2/28/2017   | NULL            | NULL         |
| 12345   | action_type_2 | 3/6/2017    | 3/3/2017        | 3            |
| 12345   | action_type_2 | 3/3/2017    | 3/25/2016       | 343          |
| 12345   | action_type_2 | 3/25/2016   | NULL            | NULL         |
| 12345   | action_type_4 | 3/6/2017    | 3/3/2017        | 3            |
| 12345   | action_type_4 | 3/3/2017    | NULL            | NULL         |
| 99887   | action_type_1 | 4/1/2017    | 2/11/2017       | 49           |
| 99887   | action_type_1 | 2/11/2017   | 1/28/2017       | 14           |
| 99887   | action_type_1 | 1/28/2017   | NULL            | NULL         |

Table：登录

| user_id | login_date |
|---------|------------|
| 12345   | 6/27/2017  |
| 12345   | 6/26/2017  |
| 12345   | 3/7/2017   |
| 12345   | 3/6/2017   |
| 12345   | 3/3/2017   |
| 12345   | 3/2/2017   |
| 12345   | 3/1/2017   |
| 12345   | 2/28/2017  |
| 12345   | 2/27/2017  |
| 12345   | 2/25/2017  |
| 12345   | 3/25/2016  |
| 12345   | 3/23/2016  |
| 12345   | 3/20/2016  |
| 99887   | 6/27/2017  |
| 99887   | 6/26/2017  |
| 99887   | 6/24/2017  |
| 99887   | 4/2/2017   |
| 99887   | 4/1/2017   |
| 99887   | 3/30/2017  |
| 99887   | 3/8/2017   |
| 99887   | 3/6/2017   |
| 99887   | 3/3/2017   |
| 99887   | 3/2/2017   |
| 99887   | 2/28/2017  |
| 99887   | 2/11/2017  |
| 99887   | 1/28/2017  |
| 99887   | 1/26/2017  |
| 99887   | 5/28/2016  |

所需输出：cnt_logins_between_action_dates 字段

| user_id | action_type   | action_date | lag_action_date | elapsed_days | cnt_logins_between_action_dates |
|---------|---------------|-------------|-----------------|--------------|---------------------------------|
| 12345   | action_type_1 | 6/27/2017   | 3/3/2017        | 116          | 5                               |
| 12345   | action_type_1 | 3/3/2017    | 2/28/2017       | 3            | 4                               |
| 12345   | action_type_1 | 2/28/2017   | NULL            | NULL         | 1                               |
| 12345   | action_type_2 | 3/6/2017    | 3/3/2017        | 3            | 2                               |
| 12345   | action_type_2 | 3/3/2017    | 3/25/2016       | 343          | 7                               |
| 12345   | action_type_2 | 3/25/2016   | NULL            | NULL         | 1                               |
| 12345   | action_type_4 | 3/6/2017    | 3/3/2017        | 3            | 2                               |
| 12345   | action_type_4 | 3/3/2017    | NULL            | NULL         | 1                               |
| 99887   | action_type_1 | 4/1/2017    | 2/11/2017       | 49           | 8                               |
| 99887   | action_type_1 | 2/11/2017   | 1/28/2017       | 14           | 2                               |
| 99887   | action_type_1 | 1/28/2017   | NULL            | NULL         | 1                               |

Answer 1

您不需要相关的子查询。使用 lag 和 join 登录 table 获取上一个日期以计算日期之间的操作。

with prev_dates as (select at.*
                    ,coalesce(lag(action_date) over(partition by user_id,action_type order by action_date)
                              ,action_date) as lag_action_date 
                    from actions_taken at
                   )
select at.user_id,at.action_type,at.action_date,at.lag_action_date
,at.action_date-at.lag_action_date as elapsed_days
,count(*) as cnt
from prev_dates at
join login l on l.user_id=at.user_id and l.login_date<=at.action_date and l.login_date>=at.lag_action_date
group by at.user_id,at.action_type,at.action_date,at.lag_action_date
order by 1,2,3

如何在不使用相关子查询的情况下有条件地计算另一个 table 中的行？

How to conditionally count rows from another table WITHOUT USING A CORRELATED SUBQUERY?

sql

netezza

correlated-subquery

aginity