哪些產品的銷售額在逐年增加？

Question

表名是SALES

**PROD_ID** **YEAR** **QUANTITY** 
    P1    2012   50 
    P1    2013   40 
    P1    2014   30 
    P2    2012   20 
    P2    2013   30 
    P2    2014   40 

輸出應該是P2但如何..？

Answer 1

這個怎麼樣？

select prod_id 
from sales 
group by prod_id 
having (sum(case when year = 2014 then quantity else 0 end) > 
     sum(case when year = 2012 then quantity else 0 end) 
     ); 

Answer 2

一個稍微複雜的方法來完成這與cte s。

Fiddle with sample data

with diff as ( 
select prod_id , 
case when quantity - nvl(lag(quantity) over(partition by prod_id order by yr),0) > 0 
then 1 else 0 end as df 
from sales 
) 
,totdiff as (select prod_id, sum(df) totdf from diff group by prod_id) 
, totals as (select prod_id, count(*) cnt from sales group by prod_id) 
select d.prod_id 
from totdiff d join totals t on t.prod_id = d.prod_id and d.totdf = t.cnt 

編輯：由@ shawnt00在comments..the查詢建議可以簡化爲

with diff as ( 
select prod_id , 
case when quantity - nvl(lag(quantity) over(partition by prod_id order by yr),0) > 0 
then 1 else 0 end as df 
from sales 
) 
select prod_id 
from diff 
group by prod_id 
having count(*) = sum(df)