希望所有不同用户的所有最新访问。

为此，我正在使用以下查询

Event.order(time: :desc).select('DISTINCT ON(user_id) user_id, time')

正在获取SQL语法错误。

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 'ON(user_id) user_id, time FROM `events` ORDER BY `events`.`time` DESC ' at line 1: SELECT  DISTINCT ON(user_id) user_id, time FROM `events` ORDER BY `events`.`time` DESC LIMIT 11)

事件表列名称

["id", "visit_id", "user_id", "name", "properties", "time"]

谁能帮我这个忙

预期的输出是这样的

{ 21 => "2018-12-18 09:44:59", 42 => "2018-12-19 12:08:59"}

21是user_id，值是上次访问时间

使用mysql作为数据库