根据另一列的优先级选择值Oracle SQL

Question

我只想为每个ID选择一个电子邮件地址，如果ID既包含工作电子邮件又包含个人电子邮件，那么我只想显示工作电子邮件。

with emails as(
select '1' id, 'work' email_type, 'abc@gmail.com' email from dual union all
select '2' id, 'work' email_type, '123@yahoo.com' email from dual union all
select '2' id, 'personal' email_type, '456@msn.com' email from dual union all
select '3' id, 'personal' email_type, 'test@work.com' email from dual
)

对于此示例，我想显示：

id    email_type    email
1     work          abc@gmail.com
2     work          123@yahoo.com
3     personal      test@work.com

Answer 1

您可以在row_number确定这些值的优先级，并获取每个ID的第一行。

select id,email_type,email
from (select id,email_type,email
      ,row_number() over(partition by id order by case when email_type='work' then 1 else 2 end) as rn
      from emails) t
where rn = 1

Answer 2

假设email_type的唯一值是work和personal，则可以使用窗口函数row_number ：

select *
from (
    select t.*,
        row_number() over (
            partition by id order by email_type desc
            ) as seqnum
    from emails t
    ) t
where seqnum = 1;

Answer 3

您可以使用子查询来确定是否有工作电子邮件。 对于样本数据，可以使用MAX函数返回“工作”类型（如果存在），如果不存在，则仅返回“个人”类型。 重新加入该链接将给出适当的结果。

WITH T1 AS (SELECT id, MAX(email_type) AS e_type FROM table_name GROUP BY id)
SELECT T1.id, T1.e_type, T2.email
FROM T1 LEFT JOIN table_name T2 ON T1.id = T2.id AND T1.e_type = T2.email_type
ORDER BY T1.id