我有一个表，记录有关电子邮件活动的事件。我想弄清楚该广告活动发生了多个事件的广告活动所占的百分比。

首先，我计算了每个广告系列中发生的事件数：

select count(*) as counter
               from campaigns_log
               where event IN ('send','open')
                 and campaign_id is not null
               group by campaign_id,email

然后，我根据是否发生多个事件来对广告系列进行分组：

select count(counter) as occurences,IF(counter > 1,2,1) as grouper
         from (select count(*) as counter
               from campaigns_log
               where event IN ('send',email) as counters_table
         group by grouper

抽样结果：

occurences ¦ grouper
132        ¦ 1
360        ¦ 2

现在，我想为每一行计算总出现次数的百分比。像这样：

occurences ¦ grouper ¦ percentage
132        ¦ 1       ¦ 132/(132+360)
360        ¦ 2       ¦ 360/(132+360)

我尝试了此操作，但是它不起作用，它不能正确计算总和：

select *,occurences/(select sum(occurences))
from (
         select count(counter) as occurences,email) as counters_table
         group by grouper
     ) as occurences_table group by occurences,grouper

你知道我最后一步的错误在哪里吗？