问题描述
我在表中有一堆学生记录。
school stduent_id start_date end_date
111 123 2010-02-03 2012-02-03
222 345 2013-02-03 2014-02-03
222 567 2015-02-03 2018-02-03
我想计算每所学校每年有多少学生,比如从 2014 年一直到 2021 年。
目前,我使用横向视图,但它是硬编码的:
SELECT school,yrs,COUNT(disTINCT stduent_id) AS cnt
FROM TABLE
LAteraL VIEW EXPLODE(ARRAY(2014,2015,2016,2017,2018,2019,2020,2021))a AS yrs
WHERE 1=1
AND YEAR(start_date) <= yrs
AND YEAR(end_date) >= yrs
我希望它在年份移动时自动更新,例如,现在应该是 2014-2021,明年应该是 2015-2022。
知道我该怎么做吗?谢谢!
解决方法
您可以使用poseexplode生成年份范围:
with year_range as(--7 years back from current year till current year
select year(current_date)-7+i as yr
from ( select posexplode(split(space(7),' ')) as (i,x)
) s
)
SELECT school,y.yr,COUNT(DISTINCT stduent_id) AS cnt
FROM TABLE
CROSS JOIN year_range y
GROUP BY school,y.yr
WHERE 1=1
AND YEAR(start_date) <= y.yr
AND YEAR(end_date) >= y.yr
,
SELECT school,yrs,COUNT(DISTINCT stduent_id) AS cnt
FROM TABLE
WHERE yrs
Between Year((DATEADD(YEAR,-7,GETDATE())))
and
Year(GETDATE())