Question

我想更新那些未购买1年的产品的价格。我该怎么做？

我目前的查询是：

UPDATE product 
   SET price = price * 0.9 
 WHERE date_purchase > SYSDATE - 365 
   AND pid IN ([How do i select the items thats not been purchased in 1year??]);

我有两张桌子：

产品=＆gt; pid，p_name等...（pid =产品ID，p_name =产品名称）
购买=＆gt; pid，date_purchase等

Answer 1

我会使用NOT EXISTS，因为它使要求更加透明。

update product 
set price = price * 0.9 
where not exists
  (select 1 from PURCHASE pchase
  WHERE pchase.pid = PRODUCT.pid
  and pchase.date_purchase > add_months(sysdate,-12))

当然，您可能想要考虑如何处理刚刚推出的产品（例如一周之久）并且从未销售过。

Answer 2

我认为这可能会接近

update product 
set price = price * 0.9 
where  pid NOT IN (
   select pr.pid 
   from product pr
   left outer join purchase pu   
   on pu.pid = pr.pid
   where (( pu.date_purchase != null) 
           AND pu.date_purchase < (SYSDATE - 365))
   or pu.pid == null
);

更新和嵌套的select语句？

2 个答案: