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我现在正在处理一个查询以获得我的用户的排名。我有两张表，一张用于用户，另一张用于利润，我保存金额和与之相关的用户 ID。通过获得一个用户产生的总利润，我需要建立一个包含三个用户的排名，排名靠前的用户对我的用户，我的用户和排名靠后的用户对我的用户。例如：

  id   |            name             | total_profit | rank
-------+-----------------------------+--------------+------
 10312 | John Doe                    |       7000.0 |    1
 10329 | Michael Jordan              |       5000.0 |    2
 10333 | Kobe Bryant                 |       4000.0 |    3
 10327 | Mike Bibby                  |       4000.0 |    3
 10331 | Phil Jackson                |       1000.0 |    4

如果我的用户是科比·布莱恩特，我需要获得迈克尔·乔丹、科比·布莱恩特和菲尔·杰克逊的排名。

如果我的用户是 Mike Bibby，我需要获得 Michale Jordan、Mike Bybby 和 Phil Jackson 的排名。

到目前为止，我有一个查询返回给我所有用户的完整排名，但我现在不知道什么是获得我想要的三个用户的好方法。我曾尝试用 ruby​​ 来做到这一点，但我认为如果我在数据库中进行所有这些处理会更好。

SELECT users.id, users.name, total_profit, rank() OVER(ORDER BY total_profit DESC)
FROM users
INNER JOIN (SELECT sum(profits.amount) AS total_profit, investor_id
          FROM profits GROUP BY profits.investor_id) profits ON profits.investor_id = users.id
ORDER BY total_profit DESC;

我正在使用 PostgresSQL 9.1.4

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2 回答 2

1 
with s as (
    select
        users.id, users.name, total_profit,
        rank() over(order by total_profit desc) as r
    from
        users
        inner join
            (
                select sum(profits.amount) as total_profit,
                investor_id
                from profits
                group by profits.investor_id
            ) profits on profits.investor_id = users.id
), u as (
    select r from s where name = 'Kobe Bryant'
)
select distinct on (r) id, name, total_profit, r
from s
where
    name = 'Kobe Bryant'
    or r in (
        (select r from u) - 1, (select r from u) + 1
    )
order by r;
于 2013-08-16T17:14:13.043 回答
0 
with cte_profits as (
    select
        sum(p.amount) as total_profit, p.investor_id
    from profits as p
    group by p.investor_id
), cte_users_profits as (
    select
        u.id, u.name, p.toral_profit,
        dense_rank() over(order by p.total_profit desc) as rnk,
        row_number() over(partition by up.total_profit order by up.id) as rn
    from users as u
        inner join cte_profits as p on p.investor_id = u.id
)
select c2.*
from cte as c
   left outer join cte as c2 on
       c2.id = c.id or
       c2.rnk = c.rnk + 1 and c2.rn = 1 or
       c2.rnk = c.rnk - 1 and c2.rn = 1
where c.name = 'Kobe Bryant'
order by c2.rnk

sql fiddle demo

于 2013-08-16T17:16:21.787 回答