Oracle SQL：一年中循环

如何解决Oracle SQL：一年中循环

我需要运行此查询以获取5年数据（2015年至2019年），我想知道是否有一种方法可以自动循环显示年份，而不是手动更改年份（例如，从2015年到2016年），并且运行此查询5次？任何帮助将不胜感激！谢谢！

Select ID,program,open_date,close_date
From clients
Where open_date=to_date('01/01/2015','mm/dd/yyyy')
 and close_date=to_date('12/31/2015','mm/dd/yyyy')

解决方法

您始终可以生成所需的日历并将其与查询一起加入。

with cal as (
  select add_months(date '2015-01-01',(level - 1)*12) as start_dt,add_months(date '2015-12-31',(level - 1)*12) as end_dt
  from dual
  connect by level <= 5
)
Select c.ID,c.program,c.open_date,c.close_date
From clients c
  join cal
    on c.open_date=cal.start_dt and c.close_date=cal.end_dt

它是行发生器。例如：

SQL> with period (start_year,end_year) as
  2    (select 2015,2020 from dual)
  3  select d.dummy,p.start_year + level - 1 as year
  4  from dual d cross join period p
  5  connect by level <= end_year - start_year
  6  order by year;

D       YEAR
- ----------
X       2015
X       2016
X       2017
X       2018
X       2019

SQL>

应用于您的代码（无法测试，没有表）：

with 
period (start_year,end_year) as
  (select 2015,2020 from dual),select c.id,c.close_date
from clients c cross join period p
where open_date  = add_months(trunc(to_date(p.start_year,'yyyy'),12 * (level - 1))
  and close_date = add_months(trunc(to_date(p.start_year,12 * (level )) - 1
connect by level <= p.end_year - p.start_year;

因为这些值产生了

SQL> with
  2  period (start_year,end_year) as
  3    (select 2015,2020 from dual)
  4  select add_months(trunc(to_date(p.start_year,12 * (level - 1)) a,5         add_months(trunc(to_date(p.start_year,12 * (level )) - 1 b
  6  from period p
  7  connect by level <= end_year - start_year;

A          B
---------- ----------
01.01.2015 31.12.2015
01.01.2016 31.12.2016
01.01.2017 31.12.2017
01.01.2018 31.12.2018
01.01.2019 31.12.2019

SQL>

看看下面的代码片段：

SELECT EXTRACT(YEAR FROM TO_DATE('01.01.2015','dd.mm.yyyy')) + ROWNUM - 1 AS "YEAR"
    FROM dual
CONNECT BY ROWNUM <= 5