Question

我正在使用mysql。我有一个名为zim_new_usa的表我想要一份所有类型为aol和gmail的电子邮件列表该表有一个名为office state

的列

美国有50个州，我希望每个州有500封电子邮件。我不知道如何在查询中编写组函数。我试图使用的查询是

select *  from zim_new_usa where 
(email like '%@aol%' or email like '%@gmail%') and length(`office state`) = 2

Answer 1

看看这里：

Using LIMIT within GROUP BY to get N results per group?

您需要为电子邮件和office_state字段提供Group by子句。

Answer 2

无法调试，但试试这个：

SET @num := 0, @state:= '';

SELECT t.email, t.`office state`, 
      @num := if(@state = t.`office state`, @num + 1, 1) AS row_number,
      @state := t.`office state` AS dummy
FROM (
  SELECT email, `office state` 
  FROM zim_new_usa 
  WHERE 
  (email LIKE '%@aol%' OR email LIKE '%@gmail%') 
 AND length(`office state`) = 2 
 ORDER BY `office state`
) as t
GROUP BY t.`office state`,t.email
HAVING row_number <= 5;

顺便说一句，尽量避免在标题表或列时使用空格。

在SQL查询组功能方面需要帮助

2 个答案: