选择所有只有一个订单并且该订单满足某些条件的用户

Question

我的表格包含这样的用户：

user_id | status
----------------
1       | 1
2       | 2
3       | 1
4       | 1

包含订单的表格

order_id | user_id | status
---------------------------
1        | 1       | 1
2        | 2       | 1
3        | 2       | 2
4        | 2       | 1
5        | 3       | 1

以及包含订购产品的表格

order_id | cash
----------------
1        | 10
1        | 20
1        | 10
2        | 10
3        | 10
3        | 10

我需要选择的是所有状态为 1 且只有一个订单且该订单的状态必须为 1 且该订单的所有产品总和必须 >=30 的用户。

所以对于上述数据查询应该只返回 id=1 的用户

我已经设法编写了选择过程，但它运行不快：

SELECT user_id
FROM   users US
WHERE  status = 1
       AND (SELECT Count(*)
            FROM   orders ORD
            WHERE  ORD.user_id = US.user_id) = 1
       AND (SELECT Count(*)
            FROM   orders ORD
            WHERE  ORD.user_id = US.user_id
                   AND ORD.status = 1) = 1
       AND (SELECT Sum(PRO.cash)
            FROM   products PRO
                   JOIN orders ORD
                     ON PRO.order_id = ORD.order_id
            WHERE  ORD.user_id = US.user_id) > 30  

我想稍微改进一下，这样我就不必使用太多内部选择了

Answer 1

您通常可以通过将查询从where 子句移动到joins 来获得更好的性能：

select  u.user_id
from    Users u
join    Orders o
on      o.user_id = u.user_id
join    Producs p
on      p.order_id = o.order_id
group by
        u.user_id
having  min(u.status) = 1 -- there's only 1 user, so min() is safe
        and count(distinct o.order_id) = 1
        and min(o.status) = 1 -- there's only 1 order, so min() is safe
        and sum(p.cash) > 30

Answer 2

SELECT USER_ID
  FROM (SELECT US.USER_ID, SUM (PRO.CASH) CASH
          FROM USERS US, ORDERS ORD, PRODUCTS PRO
         WHERE US.USER_ID = ORD.USER_ID AND ORD.ORDER_ID = PRO.ORDER_ID AND US.STATUS = 1 AND ORD.STATUS = 1)
 WHERE CASH > 30