Question

我有EmailEvent表。这是存储打开和单击的STI表（使用type属性）。我现在有这个代码，提供有关使用收件人地址（email_address字段）的电子邮件数量的信息：

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)

它会生成这样的代码：

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"

我需要提供每个email_address的打开和点击次数的信息。我无法使用count(id)，因为它会给我打开和点击，因此我需要以某种方式使用type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该怎么办？

Answer 1

替换此

count(distinct email_id) as emails_count

类似于使用case或IIF的SQLServer

sum(case when type = 'OpenEmailEvent' then 1 else 0 end)  [Opens],
sum(case when type = 'ClickEmailEvent' then 1 else 0 end)  [Click],

如何根据其他字段计算字段值？

1 个答案: