問題 ： 每4小時統計一次資料 ；

需求分析：0~23 分成6組 分別是：

 1 select id,FLOOR(id/4) hourGroup
 2 , case FLOOR(id/4)
 3         when 0 then '00:00~04:00'
 4         when 1 then '04:00~08:00'
 5         when 2 then '08:00~12:00'
 6         when 3 then '12:00~16:00'
 7         when 4 then '16:00~20:00'
 8         when 5 then '20:00~00:00' end hourRange
 
 9 from (
10 select     0    as id  union
11 select     1    as id  union
12 select     2    as id  union
13 select     3    as id  union
14 select     4    as id  union
15 select     5    as id  union
16 select     6    as id  union
17 select     7    as id  union
18 select     8    as id  union
19 select
 
     9    as id  union
20 select     10    as id  union
21 select     11    as id  union
22 select     12    as id  union
23 select     13    as id  union
24 select     14    as id  union
25 select     15    as id  union
26 select     16    as id  union
27 select     17    as id  union
28 select     18
 
    as id  union
29 select     19    as id  union
30 select     20    as id  union
31 select     21    as id  union
32 select     22    as id  union
33 select     23    as id  
34 ) t
35 order by id  ;