Question

我确信解决方案很简单，但它会让我厌烦。

表的配置如下：

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

因此，假设我正在寻找购买了以下商品的用户：

的iPod
鞋
自行车

如何构建SQL语句以返回已购买三个项目（用户必须已购买所有三个项目）的用户的user_id值？

Answer 1

加入每个项目的表格视图

需要明显，因为用户可以购买许多项目。

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

此方法也可以轻松扩展到其他项目：

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

Answer 3

最简单的解决方案是：

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)

创建SQL语句以返回购买多个项目的用户ID

3 个答案: