Question

我根据这个问题的答案进行了查询：Handling ties when ranking from the highest to the lowest

鉴于此数据集：

以下查询返回包含正确值的用户数组。

User.find_by_sql("SELECT id, score, (SELECT COUNT(DISTINCT outertable.score) + 1
FROM users WHERE score > outertable.score ORDER BY score ASC) AS rank 
FROM users as outertable GROUP BY outertable.id, outertable.score
ORDER BY score DESC LIMIT 30")

Name | Score | Rank
Mike | 5 | 1
John | 3 | 2
Mary | 3 | 2
Matt | 0 | 3

在Heroku上的Postgres中运行完全相同的查询，我收到此错误：

ActiveRecord::StatementInvalid: PGError: ERROR:  more than one row returned by a subquery used as an expression

在内部选择中添加LIMIT 1会产生以下时髦数据：

Name | Score | Rank
Mike | 5 | nil
John | 3 | 2
Mary | 3 | 2
Matt | 0 | 2

感谢您的帮助！

Answer 1

您的SQL存在一些问题。请将其改为：

SELECT  name,score, 
    (SELECT COUNT(DISTINCT score) + 1
     FROM users WHERE score > outertable.score 
     ) AS rank 
FROM users as outertable 
GROUP BY outertable.name, outertable.score
ORDER BY score DESC LIMIT 30

我已经尝试过没有任何问题！你也可以试试这句话。他们也有同样的结果。

select a.name,
       a.score,
       count(distinct b.score)+1 as rank
from 
    users a left join users b
    on a.score > b.score
group by
    a.name,a.score
order by a.score desc limit 30

生成Postgres查询返回的值不同于本地sqlite查询

1 个答案: