GROUP BY 与 ORDER BY ASC 和 DESC

Question

我有一张表spa，其中包含我需要的大部分信息：

我加入另一个表 client，以获取 last_name 字段：

我需要为每个sba_date 和provider_code 获取第一个room_code、service_detail 和provider_start_time，以及最后一个 provider_end_time。

以我的图片为例，预期的结果是：

Answer 1

您也可以使用一些 CTE 或子查询：

;WITH cte AS ( --getting min and max time for particular provider on some date
SELECT sba_date,
       MIN(provider_start_time) as provider_start_time,
       MAX(provider_end_time) as provider_end_time,
       provider_code
FROM spa
GROUP BY sba_date, provider_code
)
-- here goes join to clients (last_name) and original table to get room and detail
SELECT s.room_code,
       s.service_detail,
       c.sba_date,
       c.provider_start_time,
       c.provider_end_time,
       cl.last_name
FROM cte c
INNER JOIN client cl
   ON c.provider_code = cl.client_code
INNER JOIN spa s
   ON s.sba_date = c.sba_date0
    AND s.provider_code = c.provider_code
    AND s.provider_start_time = c.provider_start_time

Answer 2

我认为这可以通过窗口函数row_number() 和last_value() 来完成：

select
    room_code,
    service_detail,
    sba_date,
    provider_start_time,
    provider_end_time,
    last_name
from (
    select 
        s.*,
        c.last_name,
        row_number() over(
            partition by s.sba_date, s.provider_code
            order by s.provider_start_time
        ) rn,
        last_value(provider_end_time) over(
            partition by s.sba_date, s.provider_code
            order by s.provider_start_time
            range between unbounded preceding and unbounded following
        ) provider_end_time
    from spa s
    inner join client c on c.client_code = s.provider_code
) t
where rn = 1

内部查询连接两个表，并对具有相同sba_date和provider_code的记录组中的记录进行升序provider_start_time；它还计算同一组内provider_end_time 的最后一个值。然后，外部查询过滤每个组中的第一条记录。