如何根据另一个字段计算字段值？

我有EmailEvent桌子。这是存储打开和点击的 STI 表（通过使用type属性）。我现在有这个代码，它提供了有关有多少电子邮件使用收件人地址（email_address字段）的信息：

EmailEvent.where("type = 'OpenEmailEvent' OR type = 'ClickEmailEvent'")
.where(email_id: email_ids).happened_between_dates(start_date, end_date)
.select("email_address, count(distinct email_id) as emails_count")
.group(:email_address).reorder(nil)

它生成这样的代码：

SELECT email_address, count(distinct email_id) as emails_count 
FROM "email_events" 
WHERE "email_events"."deleted_at" IS NULL 
    AND (type = 'OpenEmailEvent' OR type = 'ClickEmailEvent') 
    AND "email_events"."email_id" IN (85487, 75554, 85489, 77184, 78562, 75587, 82879, 85535, 85534) 
    AND (created_at between '2017-02-28 22:52:01.000000' AND '2017-03-29 05:59:59.000000') 
GROUP BY "email_events"."email_address"

我需要提供有关每个email_address. 我不能使用，count(id)因为它会给我打开和点击，所以我需要以type某种方式使用属性，但我无法弄清楚它应该如何工作。有人可以给我建议我应该在这里做什么吗？