Oracle SQL - 如何获取具有最大日期的记录的分配 ID

Question

我正在尝试获取该职位的最后一位员工的分配 ID。那将是拥有职位或最大日期的最后一个分配。如何在以下查询中检索两者？

select max(to_char(paaf.effective_start_date, 'yyyymmdd')) || to_char(paaf.assignment_id)
from   apps.per_all_assignments_f paaf
where  paaf.position_id = 159841 
and    paaf.assignment_type in ('E', 'C')
and    paaf.primary_flag = 'Y'

我正在将最大日期转换为一个字符，以便在结果中将其子字符串化。

Answer 1

试试这个

select (paaf.assignment_id)
from   apps.per_all_assignments_f paaf
where  paaf.position_id = 159841 
and    paaf.primary_flag = 'Y'
UNION all
select (paaf.assignment_id)
from   apps.per_all_assignments_f paaf
where paaf.assignment_type in ('E', 'C')
and    paaf.primary_flag = 'Y'
AND paaf.effective_start_date = (select max(paaf.effective_start_date) from   apps.per_all_assignments_f paaf
where paaf.assignment_type in ('E', 'C')
and    paaf.primary_flag = 'Y')

Answer 2

据我所知，聚合函数返回的结果的行不能取另一个值，需要使用子查询。我认为你应该这样做：

select to_char(paaf.effective_start_date, 'yyyymmdd') || to_char(paaf.assignment_id)
from apps.per_all_assignments_f paaf
where max(to_char(paaf.effective_start_date, 'yyyymmdd')) = 
     (
         select max(to_char(paaf2.effective_start_date, 'yyyymmdd'))
         from   apps.per_all_assignments_f paaf2
         where  paaf2.position_id = 159841 
         and paaf2.assignment_type in ('E', 'C')
         and paaf2.primary_flag = 'Y'
     )

Answer 3

类似的问题可以使用 window 函数轻松解决：

select * 
from (
  select paaf.*, 
         max(paaf.effective_start_date) over (partition by position_id) as max_start_date
  from   apps.per_all_assignments_f paaf
  where  paaf.position_id = 159841 
  and    paaf.assignment_type in ('E', 'C')
  and    paaf.primary_flag = 'Y'  
) t
where effective_start_date = max_start_date;

max(paaf.effective_start_date) over (partition by position_id) as max_start_date 部分与 max(paaf.effective_start_date) ... group by position_id 部分基本相同，但不需要对整个结果进行分组。

由于您只选择了一个 position_id，因此您可以使用 over () 代替 - 但通过使用 over (partition by position_id) 查询也可以是用于检索多个职位的信息。

Answer 4

如果你只想要一个id:

SELECT  to_char(effective_start_date, 'yyyymmdd') || to_char(assignment_id)
FROM (
  select effective_start_date,
         assignment_id
  from   apps.per_all_assignments_f
  where  position_id = 159841 
  and    assignment_type in ('E', 'C')
  and    primary_flag = 'Y'
  ORDER BY effective_start_date DESC
)
WHERE ROWNUM = 1;

如果您想要所有与最新日期关联的 ID，则：

SELECT  to_char(effective_start_date, 'yyyymmdd') || to_char(assignment_id)
FROM (
  select effective_start_date,
         assignment_id,
         RANK() OVER ( ORDER BY effective_start_date DESC ) AS rnk
  from   apps.per_all_assignments_f
  where  position_id = 159841 
  and    assignment_type in ('E', 'C')
  and    primary_flag = 'Y'
  ORDER BY effective_start_date DESC
)
WHERE RNK = 1;

Answer 5

这是一个替代方法，它不需要子查询或分析函数来查找您要查找的值：

select to_char(max_effective_start_date, 'yyyymmdd') || to_char(max_row_assignment_id)
from   (select max(paaf.effective_start_date) max_effective_start_date,
               max(paaf.assignment_id) keep (dense_rank first order by effective_start_date desc) max_row_assignment_id
        from   apps.per_all_assignments_f paaf
        where  paaf.position_id = 159841 
        and    paaf.assignment_type in ('E', 'C')
        and    paaf.primary_flag = 'Y');

Oracle SQL - 如何获取具有最大日期的记录的分配 ID

Oracle SQL - How to get the assignment id of the record with the maximum date

sql

oracle

greatest-n-per-group