获取每个类别的最新状态

Question

我遇到了这个有趣的问题。我有一个名为 email_track 的 table 来跟踪每个类别的电子邮件状态，比如（邀请、时事通讯）

这是我的 table 数据的样子，

通过以下查询，我可以获得每个 to_email、

的最新记录

with `et2` as (
    select `et1`.`category`, `et1`.`to_email`, `et1`.`subject`, `et1`.`status`, ROW_NUMBER() OVER (partition by `to_email` order by `id` desc) as `rn`
    from `email_track` `et1`
)
select * from `et2` where `rn` = 1;

select `et1`.`category`, `et1`.`to_email`, `et1`.`subject`, `et1`.`status`, `et2`.`id`
from `email_track` `et1`
left join `email_track` `et2` on (`et1`.`to_email` = `et2`.`to_email` and `et1`.`id` < `et2`.`id`)
where `et2`.`id` is null;

我期待的是电子邮件 john@example.com 我应该得到两条记录，一条是类别邀请，另一条是时事通讯。现在，我们不会得到那个结果，因为我们按 to_email 分区

Answer 1

I should get two records one for category invitation and the other for the newsletter. Now, we won't get that result since we partition by to_email.

将 category 添加到 window 函数的 partition by 子句应该足以提供您想要的结果：

with et2 as (
    select et1.category, et1.to_email, et1.subject, et1.status, 
        row_number() over(partition by to_email, category order by id desc) as rn
    from email_track et1
)
select * from et2 where rn = 1;