Question

mysql> describe events;
+-----------------+--------------+------+-----+---------+----------------+
| Field           | Type         | Null | Key | Default | Extra          |
+-----------------+--------------+------+-----+---------+----------------+
| id              | int(11)      | NO   | PRI | NULL    | auto_increment |
| city_id         | int(11)      | NO   | MUL | NULL    |                |

以下sql导致错误。

  SELECT CONCAT_WS('',users.fname,' ', users.lname) as user_name,
   COUNT(events.id) AS events_count
  FROM users
   INNER JOIN events ON users.id = events.user_id
   INNER JOIN cities ON cities.id = events.city_id
  GROUP BY
    users.id
  WHERE
    events.city_id = 18
  ORDER BY
   COUNT(events.id) DESC
  LIMIT 10

错误

ActiveRecord::StatementInvalid: Mysql2::Error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'WHERE
        events.city_id = 18

如果我删除了WHERE子句，那么一切正常。

Answer 1

尝试将WHERE子句放在GROUP BY

之前

Answer 2

在GROUP BY之前使用WHERE，它应该可以工作

Answer 3

WHERE需要在GROUP BY

之前出现

Answer 4

将events.city_id=18条件放入JOIN中。因为你正在进行INNER连接，所以没有理由在WHERE子句中使用它。

INNER JOIN events ON users.id = events.user_id AND events.city_id=18

Answer 5

您的意思是使用GROUP BY...HAVING吗？

来自mysql的子句问题

5 个答案: