使用行号的 PostgreSQL 百分比变化

Question

我正在尝试使用 PostgreSQL 的行号来查找百分比变化，但我遇到了一个错误，我的“percent_change”列显示为 0。

这是我的代码。

WITH CTE AS (
SELECT date, sales, ROW_NUMBER() OVER (ORDER by date) AS rn
FROM sales_2019)

SELECT c1.date, c1.sales,
CAST(COALESCE (((c1.sales - c2.sales) * 1.0 / c2.sales) * 100, 0) AS INT) AS percent_change
FROM CTE AS c1
LEFT JOIN CTE AS c2 
ON c1.date = c2.date AND c1.rn = c2.rn + 1

这是我的SQL table，以备不时之需。提前谢谢你，非常感谢。

Answer 1

您可以使用 LAG() 来满足您的要求：

select 
date, 
sales, 
round(coalesce((((sales-(lag(sales) over (order by date)))*1.0)/(lag(sales) over (order by date)))*100,0),2)
                                                            
from sales_2019

或者你可以试试WITH 子句

with cte as ( select
  date,
  sales,
  coalesce(lag(sales) over (order by date),0) as previous_month
                            from sales_2019
  )
select 
date,
sales,
round( coalesce( (sales-previous_month)*1.0/nullif(previous_month,0),0 )*100,2)
from cte
           

DEMO

根据评论中的要求进行编辑

with cte as ( select
  date_,
  sales,
  ROW_NUMBER() OVER (ORDER by date_) AS rn1,
  ROW_NUMBER() OVER (ORDER by date_)-1 AS rn2
                            from sales_2019
  )
  
  select t1.date_,
  t1.sales,
  round( coalesce( (t1.sales-t2.sales)*1.0/nullif(t2.sales,0),0 )*100,2)
  from cte t1 left join cte t2 on t1.rn2=t2.rn1

DEMO