Oracle查詢問題

Question

請讓我知道爲什麼這個查詢不能一起工作。他們分別工作：

( (select item_name, 
      sum(p_qty) 
     from stock 
    where p_date between '08/06/2010' and '08/07/2010' 
    group by item_name) - 
( select item_name, 
      sum(p_r_qty) 
     from stock 
    where p_r_date between '08/06/2010' and '08/07/2010' 
    group by item_name)) 

Answer 1

select item_name, 
      sum(p_qty) , 
      sum(p_r_qty) 
     from stock 
    where p_date between '08/06/2010' and '08/07/2010' 
group by item_name 

這是你想要的嗎？

select item_name, 
      sum(p_qty)-sum(p_r_qty) 
     from stock 
    where p_date between '08/06/2010' and '08/07/2010' 
group by item_name