仅获取数据为最大值的行

Question

我有一个 table 这样的：

treatment | patient_id
        3 |          1
        3 |          1
        3 |          1
        2 |          1
        2 |          1
        1 |          1
        2 |          2
        2 |          2
        1 |          2

我只需要像这样获取 max(treatment) 上的行：

treatment | patient_id
        3 |          1
        3 |          1
        3 |          1
        2 |          2
        2 |          2

patient_id 1 max(treatment) 是 3 patient_id 2 max(treatment) 是 2

Answer 1

例如，您可以使用最大值加入聚合 table：

select t.*
from tmp t
inner join (
  select max(a) max_a, b
  from tmp
  group by b
) it on t.a = it.max_a and t.b = it.b;

Here's 数据库 fiddle.

Answer 2

试试这个：

WITH list AS
( SELECT patient_id, max(treatment) AS treatment_max
    FROM your_table
   GROUP BY patient_id
)
SELECT *
  FROM your_table AS t
 INNER JOIN list AS l
    ON t.patient_id = l.patient_id
   AND t.treatment = l.treatment_max

Answer 3

您可以使用 rank:

with u as
(select *, rank() over(partition by patient_id order by treatment desc) r
from table_name)
select treatment, patient_id
from u
where r = 1;

Fiddle

Answer 4

使用相关子查询

select t1.* from table_name t1
where t1.treatment=( select max(treatment) from table_name t2 where t1.patient_id=t2.patient_id
)

仅获取数据为最大值的行

Get only rows where data is the max value

sql

postgresql

greatest-n-per-group