Question

我在db2中有一个包含列的表：

PK (varchar)
COLUMN1 (VARCHAR)
..
..
..
CREATION_TIMESTAMP (TIMESTAMP)

我需要根据每五天一次的自定义日期范围计算。我将从“2014年12月1日”开始，然后根据5天的差距对我的计数进行分组：

group 1 : Dec 1 to Dec 5
group 2 : Dec 6 to Dec 10
...
...
and so on.

如果我必须按预先定义的范围进行分组，这很容易;我可以简单地做

select count(*), week(CREATION_TIMESTAMP) 
from  MYTABLE 
group by week(CREATION_TIMESTAMP);

类似于日，月，年等。但是有没有办法定义上面提到的自定义范围？

Answer 1

您需要一个将creation_time映射到所需间隔的函数。类似的东西：

select monthname(CREATION_TIMESTAMP)
     , day(CREATION_TIMESTAMP) + 1 - mod(day(CREATION_TIMESTAMP),5)
     , count(1)
from ...
group by monthname(CREATION_TIMESTAMP)
    , day(CREATION_TIMESTAMP) + 1 - mod(day(CREATION_TIMESTAMP),5)

示例：

with t(n) as  ( values date('2014-12-01') 
                union all 
                select n + 1 day from t 
                where n < '2014-12-20'
              ) select distinct day(n) + 1 - mod(day(n),5), day(n) + 5 - mod(day(n),5) 
                from t;

1           2          
----------- -----------
SQL0347W  The recursive common table expression "LELLE.T" may contain an 
infinite loop.  SQLSTATE=01605

      1           5
      6          10
     11          15
     16          20
     21          25

编辑：扩展示例

with t(n) as  ( 
    values date('2014-12-01') 
    union all 
    select n + 1 day 
    from t where n < '2014-12-20' 
) 
select day(n)
     , mod(day(n),5)
     , day(n) + 1 - mod(day(n),5) 
from t

      1           1           1
      2           2           1
      3           3           1
      4           4           1
      5           0           6
      6           1           6
      7           2           6
      8           3           6
      9           4           6
     10           0          11
     11           1          11
     12           2          11
     13           3          11
     14           4          11
     15           0          16
     16           1          16
     17           2          16
     18           3          16
     19           4          16
     20           0          21

数据库db2：按自定义日期范围分组

1 个答案: