SQL min/max分组问题

Question

我有类似以下数据结构:

Category    StartDateTime       EndDateTime
===============================================
1           12/1/2009 12:00     12/1/2009 12:12
1           12/1/2009 04:00     12/1/2009 04:20
2           12/2/2009 10:15     12/2/2009 10:22
2           12/2/2009 11:00     12/2/2009 11:01

我想要每个类别的最小StartDateTime和最大EndDateTime.像这样:

Category    MinStartDateTime    MaxEndDateTime
===============================================
1           12/1/2009 12:00     12/1/2009 04:20
2           12/2/2009 10:15     12/2/2009 11:01

使用按类别分组的最小值和最大值似乎不起作用:

select
    Category,
    min(StartDateTime) [MinStartDateTime],
    max(EndDateTime) [MaxDateTime]
from
    MyTable
group by
    Category
order by
    Category,
    StartDateTime,
    EndDateTime

我还在每个min和max语句的子查询中尝试了两个内部联接,但它似乎排除了一些记录:

select distinct
    T1.Category,
    T1.StartDateTime [MinStartDateTime],
    T1.EndDateTime [MaxEndDateTime]

from
    MyTable T1

inner join
    (select
        Category,
        min(StartDateTime) [MinStartDateTime]
     from
        MyTable
     group by
        Category) T2
on T2.Category = T1.Category and T2.MinStartDateTime = T1.StartDateTime

inner join
    (select
        Category,
        max(EndDateTime) [MaxEndDateTime]
     from
        MyTable
     group by
        Category) T3
on T3.Category = T1.Category and T3.MaxEndDateTime = T1.EndDateTime

order by
    T1.Category,
    T1.encodeStartDateTime,
    T1.encodeEndDateTime

有任何想法吗？数据库是Sybase ASE,应该符合SQL-92.

Answer 1

您的第一个解决方案看起来正确,除了order by子句; 尝试:

select
    Category,
    min(StartDateTime) [MinStartDateTime],
    max(EndDateTime) [MaxDateTime]
from MyTable
group by
    Category
order by
    Category,
    MinStartDateTime,
    MaxDateTime