sql - SQL Select 语句 - 多个输出列

Question

假设我收到这样的查询：

select count(*) as Morning from Table 
where timestamp between '01.08.13 06:00:00' AND '01.08.13 10:00:00'

现在我想有一个中午和晚上的输出。是的，我可以做三个查询，但是是否可以创建一个返回所有三个（早上、中午、晚上）的 select 语句？

Answer 1

select sum(case when timestamp between '01.08.13 06:00:00' 
                                   and '01.08.13 10:00:00'
                then 1 
                else 0 
           end) as Morning,
       sum(case when timestamp between '01.08.13 10:00:00' 
                                   and '01.08.13 14:00:00'
                then 1 
                else 0 
           end) as Noon,
       sum(case when timestamp between '01.08.13 14:00:00'
                                   and '01.08.13 18:00:00'
                then 1 
                else 0
           end) as Evening
from Table