我很难从SQL数据库获取信息。
我正在使用的表如下所示：
Table: system.episode_history
+------------+----------------+------------+----------------+
| patient_id | episode_number | admit_date | discharge_date |
+------------+----------------+------------+----------------+
| 111 | 4 | 01/05/2017 | |
+------------+----------------+------------+----------------+
| 222 | 8 | 03/17/2017 | |
+------------+----------------+------------+----------------+
| 222 | 9 | 03/20/2017 | |
+------------+----------------+------------+----------------+
| 333 | 2 | 10/08/2017 | |
+------------+----------------+------------+----------------+
| 444 | 7 | 08/09/2017 | 08/20/2017 |
+------------+----------------+------------+----------------+
Table: system.view_episode_summary_current
+------------+----------------+------------+----------------------+
| patient_id | episode_number | admit_date | last_date_of_service |
+------------+----------------+------------+----------------------+
| 111 | 4 | 01/05/2017 | 11/01/2017 |
+------------+----------------+------------+----------------------+
| 222 | 8 | 03/17/2017 | 11/03/2017 |
+------------+----------------+------------+----------------------+
| 222 | 9 | 03/20/2017 | 11/04/2017 |
+------------+----------------+------------+----------------------+
| 333 | 2 | 10/08/2017 | 11/05/2017 |
+------------+----------------+------------+----------------------+
Table: system.history_attending_practitioner
+------------+----------------+---------------------+-----------------------+
| patient_id | episode_number | attend_practitioner | pract_assignment_date |
+------------+----------------+---------------------+-----------------------+
| 111 | 4 | 4444 | 01/05/2017 |
+------------+----------------+---------------------+-----------------------+
| 222 | 8 | 5555 | 03/17/2017 |
+------------+----------------+---------------------+-----------------------+
| 222 | 8 | 6666 | 03/20/2017 |
+------------+----------------+---------------------+-----------------------+
| 222 | 9 | 7777 | 04/10/2017 |
+------------+----------------+---------------------+-----------------------+
| 333 | 2 | 5555 | 10/08/2017 |
+------------+----------------+---------------------+-----------------------+
| 444 | 7 | 7777 | 08/09/2017 |
+------------+----------------+---------------------+-----------------------+
Table: system.user_practitioner_assignment
+------------+----------------+---------------------+--------------------+
| patient_id | episode_number | backup_practitioner | date_of_assignment |
+------------+----------------+---------------------+--------------------+
| 111 | 4 | | |
+------------+----------------+---------------------+--------------------+
| 222 | 8 | 7777 | 03/17/2017 |
+------------+----------------+---------------------+--------------------+
| 222 | 8 | 4444 | 05/18/2017 |
+------------+----------------+---------------------+--------------------+
| 222 | 9 | | |
+------------+----------------+---------------------+--------------------+
| 333 | 2 | 4444 | 10/08/2017 |
+------------+----------------+---------------------+--------------------+
| 333 | 2 | 5555 | 10/19/2017 |
+------------+----------------+---------------------+--------------------+
我需要SQL查询来返回这样的表：
+-------------+------------+----------------+------------+--------------------+----------------------+
| {?Staff_ID} | patient_id | episode_number | admit_date | date_of_assignment | last_date_of_service |
+-------------+------------+----------------+------------+--------------------+----------------------+
| 4444 | 111 | 4 | 01/05/2017 | 01/05/2017 | 11/01/2017 |
+-------------+------------+----------------+------------+--------------------+----------------------+
| 4444 | 222 | 8 | 03/17/2017 | 05/18/2017 | 11/03/2017 |
+-------------+------------+----------------+------------+--------------------+----------------------+
我正在使用system.episode_history表来确定该剧集是否有出院日期。
位置（system.episode_history.discharge_date为NULL）
我正在使用system.view_episode_summary_current表获取与剧集相关的服务的最后日期。
我尝试了几件事，但没有成功。
首先，SQL处理程序似乎对查询中的别名无所适从。我还不知道如何安抚它。
第二，SQL句柄似乎已经足够老了，以至于它不知道如何处理OVER，LAG（），LEAD（）等SQL窗口函数。因此，我只想弄清楚如何与MAX（）函数一起使用自联接。我认为这是一台较旧的SAP SQL服务器。
我是SQL的新手。例如，根据我观察到的情况，我假设SQL查询中的大写字母（大部分）是不相关的，但我不确定。我一直在互联网上寻求帮助，但没有发现任何可以使我工作或理解的有用信息（在这一点上，大多数感觉像是外语）。我在工作内部和外部都知道SQL的人很困惑，但这是事实。我不在这里，请帮忙。
更新1
我对下面的建议查询进行了调整，直到没有错误为止，并最终得到了如下查询：
select staff.staff_id, epi.patient_id, epi.episode_number as episode_id, epi.admit_date, staff.date_of_assignment, curr.last_date_of_service
from system.episode_history as epi
join (
select patient_id, episode_number, attend_practitioner as staff_id, pract_assignment_date as date_of_assignment
from system.history_attending_practitioner
union
select patient_id, episode_number, backup_practitioner as staff_id, date_of_assignment as date_of_assignment
from system.user_practitioner_assignment
where (backup_practitioner is not null)
) as staff on staff.patient_id=epi.patient_id and staff.episode_number=epi.episode_number
and not exists(select * from system.history_attending_practitioner as a2 where a2.patient_id=staff.patient_id and a2.episode_number=staff.episode_number and a2.pract_assignment_date>staff.date_of_assignment)
and not exists(select * from system.user_practitioner_assignment as a3 where a3.patient_id=staff.patient_id and a3.episode_number=staff.episode_number and a3.date_of_assignment>staff.date_of_assignment)
join system.view_episode_summary_current curr on curr.patient_id=epi.patient_id and curr.episode_number=e.episode_number
where (epi.discharge_date is null)
and staff.staff_id = '4444'
当我对真实数据库运行此查询时，它正确地从system.history_attending_practitioner返回4个匹配项，但仅从system.user_practitioner_assignment返回8个匹配项中的1个。充其量，我以前的许多尝试只返回了一个表或另一个表的结果，但从未同时返回。因此，至少这是一个改进。
更新2
调整查询项目的顺序后，这是返回正确结果的版本：
select staff.staff_id, epi.patient_id, epi.episode_number as episode_id, epi.admit_date, staff.date_of_assignment, curr.last_date_of_service
from system.episode_history as epi
join (
select patient_id, episode_number, attend_practitioner as staff_id, pract_assignment_date as date_of_assignment
from system.history_attending_practitioner
where (attend_practitioner is not null)
and not exists(select * from system.history_attending_practitioner as a2 where a2.patient_id=system.history_attending_practitioner.patient_id and a2.episode_number=system.history_attending_practitioner.episode_number and a2.pract_assignment_date>system.history_attending_practitioner.pract_assignment_date)
union
select patient_id, episode_number, backup_practitioner as staff_id, date_of_assignment as date_of_assignment
from system.user_practitioner_assignment
where (backup_practitioner is not null)
and not exists(select * from system.user_practitioner_assignment as a3 where a3.patient_id=system.user_practitioner_assignment.patient_id and a3.episode_number=system.user_practitioner_assignment.episode_number and a3.date_of_assignment>system.user_practitioner_assignment.date_of_assignment)
) as staff on staff.patient_id=epi.patient_id and staff.episode_number=epi.episode_number
join system.view_episode_summary_current curr on curr.patient_id=epi.patient_id and curr.episode_number=e.episode_number
where (epi.discharge_date is null)
and staff.staff_id = '4444'
答案 0 :(得分：0)
根据您的问题很难解决。我想您需要为每个患者/病历分配最新任务。
您可以使用max使用第二个子查询来执行此操作，也可以按照以下方式使用不存在。
正如您所提到的，使用row_number（）和/或CTE会容易得多，但这是批量标准sql版本。
select s.staff_id, e.patient_id, e.episode_number as episode_id, e.admit_date, s.date_of_assignment, c.last_date_of_service
from episode_history e
join (
select patient_id, episode_number, attend_practitioner as staff_id, pract_assignment_date as date_of_assignment
from history_attending_practitioner
union
select patient_id, episode_number, backup_practitioner as staff_id, date_of_assignment as date_of_assignment
from user_practitioner_assignment
where backup_practitioner is not null
) s on s.patient_id=e.patient_id and s.episode_number=e.episode_number
and not exists(select * from history_attending_practitioner a2 where a2.patient_id=s.patient_id and a2.episode_number=s.episode_number and a2.pract_assignment_date>s.date_of_assignment)
and not exists(select * from user_practitioner_assignment a3 where a3.patient_id=s.patient_id and a3.episode_number=s.episode_number and a3.date_of_assignment>s.date_of_assignment)
join view_episode_summary_current c on c.patient_id=e.patient_id and c.episode_number=e.episode_number
where e.discharge_date is null