Question

我正在尝试从外部查询的每一行获取一个concat列表，但我在其他地方得到Unknown column 'outter_client' in 'where clause'我看到你无法从子查询中访问外部变量，有没有办法重新编写这个查询没有存储过程，视图或临时表，并让它工作？

SELECT client AS outer_client, top_domain
FROM log
JOIN (
   SELECT GROUP_CONCAT(t.domain) AS top_domain 
   FROM (
      SELECT domain 
      FROM log
      WHERE client = outer_client 
      GROUP BY 1 
      ORDER BY SUM(bytes)
      LIMIT 5
   ) t
) k
GROUP BY client
ORDER BY SUM(bytes)
LIMIT 5;

Answer 1

我认为您希望每个客户端的前五个域基于字节数。您可以使用嵌套选择和substring_index() / group_concat()技巧来执行此操作：

select client,
       substring_index(group_concat(domain order by sumbytes desc), ',', 5) as top5domains
from (select client, domain, sum(bytes) as sumbytes
      from log
      group by client, domain
     ) cd
group by client
order by sum(sumbytes) desc
limit 5;

来自子查询的MySQL GROUP_CONCAT

1 个答案: