通过 Max DateTime 字段提取单个记录的子查询

Question

我有一个子查询 (MS SQL 2016) 来提取特定度量的最新度量值。我需要通过 PAT_ID 将结果度量值链接回我的主查询。我遇到的问题是我无法让 MAX Date（最近的日期）在子查询中只提取一条记录。

以下查询返回大量记录，而不仅仅是最近的记录

    SELECT distinct meas.MEAS_VALUE, rec.pat_id, MAX(meas.ENTRY_TIME) "MAX ET"
    from ip_flwsht_rec rec
        inner join [CLARITY].[dbo].[IP_FLWSHT_MEAS] meas on rec.fsd_id=meas.FSD_ID 
            and meas.flo_meas_id='14' 
            and meas.MEAS_VALUE is not null
    where meas.ENTRY_TIME>=(DATEADD(day, DATEDIFF(day, 0,getdate()) - 548, 0))
        AND rec.pat_id = 'CENSORED'
    GROUP BY meas.MEAS_VALUE, rec.PAT_ID 

这会返回结果...

同一位患者有 9 个结果，但我只想要最近的。不知道我做错了什么，非常感谢任何帮助。

Answer 1

根据您的要求，@Zack 的答案中的top 1 方法可能是最好的方法。它具有所有品质中最具救赎性的特点之一，即简单。

如果top 1 方法不能满足您的要求，那么您非常接近。在你的问题中，你说，I need to link the resulted measure value back to my main query by PAT_ID。实际上，您需要将其与 pat_id 和 entry_time 两个字段链接起来。

为确保您只为每位患者获取一份记录，请更改以下内容：

SELECT distinct meas.MEAS_VALUE, rec.pat_id, MAX(meas.ENTRY_TIME) "MAX ET"

到这里：

SELECT rec.pat_id, MAX(meas.ENTRY_TIME) "MAX ET"

您的最终查询类似于以下内容：

with mostRecentRecords as (
select rec.pat_id, MAX(meas.ENTRY_TIME) mostRecentEntry
from etc
group by rec.pat_id
)
select whatever
from your tables
join mostRecentRecords on rec.pat_id = mostRecentRecords.pat_id
     and meas.entry_time = mostRecentEntry

Answer 2

只需在您的选择中添加 TOP(1)，然后按时间排序：

SELECT distinct TOP(1) meas.MEAS_VALUE, ...
...
ORDER BY meas.ENTRY_TIME DESC

Answer 3

在加入之前使用row_number() 对meas 记录进行排序，并按fsd_id 进行分区。无需 group by 或聚合，即可为每个 fds_id 生成来自 meas 的最新记录。

select
    meas.MEAS_VALUE
  , rec.pat_id
  , [Max ET] = meas.ENTRY_TIME
from ip_flwsht_rec rec
  inner join (
    select *
      , rn = row_number() over (partition by fsd_id order by ENTRY_TIME desc)
    from [CLARITY].[dbo].[IP_FLWSHT_MEAS]
    ) as meas 
        on rec.fsd_id=meas.FSD_ID 
       and meas.rn = 1 /* just the latest row based on `entry_time` */
       and meas.flo_meas_id='14' 
       and meas.MEAS_VALUE is not null
where meas.ENTRY_TIME>=(dateadd(day, datediff(day, 0,getdate()) - 548, 0))
    and rec.pat_id = 'CENSORED'