僅減少1個表中日期的差異數據Oracle SQL

Question

我有一個表COSTS包含PART_NO,ITEM_COSTS,COST_DATE。

如何從不同日期扣除成本？這基本上是我啥子想

Select PART_NO 
, ITEM_COSTS 
WHERE COST_DATE = DATE_A 
AND PART_NO = B 

和減去從

Select PART_NO 
, ITEM_COSTS 
WHERE COST_DATE = DATE_B 
AND PART_NO = B 

Answer 1

SELECT a.part_no, 
     b.item_costs - a.item_costs as diff 
FROM costs a 
    JOIN costs b ON a.part_no = b.part_no 
WHERE a.cost_date = date_a 
    AND b.cost_date = date_b