分开记录最大日期

Question

Metal帮助我编写了如下的SQL

select id  
        , OrderDate
        , RejectDate
        , max(case when RejectDate = '1900-01-01' then '9999-12-31' else RejectDate end) as rSum
     from tableA
     group by id, OrderDate, RejectDate

现在，我想找出低于最大拒绝日期的特定ID的所有记录，以将它们从转换表中删除

Answer 1

一种选择是使用row_number()：

select 
    id,  
    OrderDate,
    RejectDate
from (
    select 
        t.*,
        row_number() over(
            partition by id
            order by case when RejectDate = '1900-01-01' then '9999-12-31' else RejectDate end desc
        ) rn
    from tableA t
) t
where rn > 1

该技术的优势在于它避免了聚合，而聚合可能会导致更好的性能。另外，您可以利用可更新CTE的概念轻松地将其转换为delete语句，如下所示：

with cte as (
    select 
        row_number() over(
            partition by id
            order by case when RejectDate = '1900-01-01' then '9999-12-31' else RejectDate end desc
        ) rn
    from tableA t
)
delete from cte where rn > 1

Answer 2

这应该有效...

SELECT *
FROM tableA t1
INNER JOIN (
    SELECT ID, MAX(RejectDate) as MaxRejectDate
    FROM tableA) t2 ON t1.ID = t2.ID
WHERE t1.RejectDate < t2.MaxRejectDate