創建一個SQL語句返回購買多件商品

Question

我敢肯定，解決方法很簡單，但它迴避了我的用戶ID。

一臺配置，像這樣：

TABLE NAME = sales 
Field 1 = id INT Auto Increment Primary Key 
Field 2 = user_id INT NOT NULL 
Field 3 = item VARCHAR(100) NOT NULL 

所以我們可以說我在找的是已購買下列項目的用戶：

• 的iPod
• 鞋
• 自行車

將如何我構造了一個SQL語句來返回已購買這三項中每一項的用戶的user_id值（用戶必須購買了全部三項）？

Answer 1

加入了意見表中的每個項目

需要不同的用戶可以買到許多一個項目。

select distinct(ipod.user_id) 
from sales ipod 
    inner join sales shoes on shoes.user_id = ipod.user_id 
    inner join sales bike on bike.user_id = ipod.user_id 
where ipod.item = 'ipod' 
    and shoes.item = 'shoes' 
    and bike.item = 'bicycle' 

Answer 2

最簡單的解決方案如下。

select user_id 
from sales s1 
where exists (select user_id from sales s2 
       where item = 'ipod' and s2.user_id = s1.user_id) 
and exists (select user_id from sales s2 
       where item = 'shoes' and s2.user_id = s1.user_id) 
and exists (select user_id from sales s2 
       where item = 'bycycle' and s2.user_id = s1.user_id) 

Answer 3

這種方法應該可以很容易地擴展到其他的東西：

select USER_ID, count(distinct ITEM) 
    from SALES 
    where ITEM in ('ipod', 'shoes', 'bicycle') 
group by USER_ID 
    having count(distinct ITEM) = 3