database - IBM DB2 PIVOT 一个完整的日期表

Question

我在 DB2 中有这张表：

   DATE
----------
09/11/2021
06/10/2021
28/11/2021
17/11/2021
11/10/2021
24/11/2021
07/11/2021
30/11/2021

我想计算一个日期在表格中出现的次数，并按年和月分组，并显示如下：

| YEAR | OCTOBER | NOVEMBER |
----------------------------
| 2021 |    2    |    6     |

标签： databasedatedb2db2-400db2-luw

Answer 1

由于月份是一个已知数量，您可以使用案例语句的总和：

select year(datecol) as year
  ,sum(case when month(datecol) = 1 then 1 else 0 end) as jan
  ,sum(case when month(datecol) = 2 then 1 else 0 end) as feb
  ,sum(case when month(datecol) = 3 then 1 else 0 end) as mar
  ,sum(case when month(datecol) = 4 then 1 else 0 end) as apr
  ,sum(case when month(datecol) = 5 then 1 else 0 end) as may
  ,sum(case when month(datecol) = 6 then 1 else 0 end) as jun
  ,sum(case when month(datecol) = 7 then 1 else 0 end) as jul
  ,sum(case when month(datecol) = 8 then 1 else 0 end) as aug
  ,sum(case when month(datecol) = 9 then 1 else 0 end) as sep
  ,sum(case when month(datecol) = 10 then 1 else 0 end) as oct
  ,sum(case when month(datecol) = 11 then 1 else 0 end) as nov
  ,sum(case when month(datecol) = 12 then 1 else 0 end) as dec
 from datetest 
 group by year(datecol)
 order by 1;

这将为您提供与此类似的输出：

YEAR        JAN         FEB         MAR         APR         MAY         JUN         JUL         AUG         SEP         OCT         NOV         DEC
----------- ----------- ----------- ----------- ----------- ----------- ----------- ----------- ----------- ----------- ----------- ----------- -----------
       2018           0           0           0           0           0           0           0           0           0           0           3           0
       2019           0           0           0           0           0           0           0           0           0           1           2           0
       2020           0           0           0           0           0           0           0           0           0           1           1           0
       2021           0           0           0           0           0           0           0           0           0           2           6           0