在PostgreSQL

Question

我試圖創建一個表，看起來像這樣（過去12個月的表）

month, year 
10, 2016 
9, 2016 
8, 2016 
7, 2016 
6, 2016 
5, 2016 
4, 2016 
3, 2016 
2, 2016 
1, 2016 
12, 2015 
11, 2015 

我的代碼看起來像這樣創建過去12個月的表：

select date_part('month', current_date) as order_month, 
select date_part('year', current_date) as order_year 
union all 
select date_part('month', current_date - interval '1 month') as order_month, 
select date_part('year', current_date - interval '1 month') as order_year 
union all 
... 

有沒有更簡潔的寫作方式，而不是使用11個聯合？

Answer 1

generate_series(start, stop, step)將是有益的，使得

SELECT 
    EXTRACT('month' FROM d) AS month, 
    EXTRACT('year' FROM d) AS year 
FROM 
    GENERATE_SERIES(
     now(), 
     now() - interval '12 months', 
     interval '-1 month' 
    ) AS d 
;