Question

让我们知道我有这个table_1：

Year Item Qty_sold
2013 1    3
2013 2    2
2013 3    5
2014 1    2
2014 2    3

我会做这样的事情

select year , sum(Qty_sold) as Quantity
from table_1 inner join table_2 on .... inner join table_n
where Year = 2014

最终结果主要取决于按年度划分的过滤器，但还有其他表格。

但结果我需要这样的东西：

Year Quantity  Diff_Percentage
2014 5         0.5

因为在上一年（2013年），所售商品的最终数量为10个。

此致

Answer 1

你似乎想要这样的东西：

select year, sum(Qty_sold) as Quantity,
       lag(sum(qty_sold)) over (order by year) as prev_Quantity,
       (1 - Quantity / lag(sum(qty_sold)) over (order by year)) as diff_percentage
from table
group by Year;

当然，这会返回所有年份的信息。如果您真的只想要2014年和2013年，那么使用条件聚合：

select year,
       sum(case when year = 2014 then Qty_sold end) as Quantity_2014,
       sum(case when year = 2013 then Qty_sold end) as Quantity_2013,
       (1 - sum(case when year = 2014 then Qty_sold end)/
            sum(case when year = 2013 then Qty_sold end) 
       ) as diff_percentage
from table
where Year in (2013, 2014);

我有点猜测diff_percentage的公式，但我认为这就是你想要的。

Answer 2

根据您的要求，请尝试此

select t.year,qty, (1-qty/prev_qty)
from
(select year, sum(Qty_sold) as qty,
       lag(sum(qty_sold)) over (order by year) as prev_qty
from tbl group by Year) t where t.year=in_year --in_year whichever year record you want.

希望它适合你。

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