Question

见下表

Email  Post_Year  country
====== ========== =======
a@a.com  2006       US
a@a.com  2007       US
a@a.com  2008       HK1
a@a.com  2008       HK
b@b.com  2009       CN
b@b.com  2010       SW

我想要

通过电子邮件发送最大Post_year组的所有列，如果有多个最大Post_year，只需选择一个
以及该特定电子邮件的max（post_year）-min（post_year）的num_of_yrs。

Email  Post_Year  country  Num_Of_Yrs
====== ========== ======= =============
a@a.com  2008      HK       2 [which is 2008-2006]
b@b.com  2010      SW       1 [which is 2010-2009]

如何达到目的？

Answer 1

编辑：根据您编辑的意图，您只需使用：

SELECT 
    email, 
    MAX(post_year) post_year,
    MAX(country) country, 
    MAX(post_year) - MIN(post_year) num_of_yrs
FROM 
    table_name
GROUP BY 
    email;

你可以用这个：

WITH tmp AS
(
    SELECT 
        email, 
        MAX(post_year) max_post_year,
        MIN(post_year) min_post_year
    FROM 
        table_name
    GROUP BY 
        email
)
SELECT 
    t.email,
    t.post_year,
    t.country,
    tmp.max_post_year - tmp.min_post_year num_of_yrs
FROM 
    table_name t
INNER JOIN 
    tmp
ON t.email = tmp.email
    AND t.post_year = tmp.max_post_year;

Answer 2

您可以使用窗口函数row_number获取一行，每封电子邮件的最大年份和窗口函数max和min，以获得每封电子邮件的最大差异。

试试这个：

select *
from (
    select t.*,
        row_number() over (partition by email 
                            order by post_year desc) rn,
        max(post_year) over (partition by email) -
        min(post_year) over (partition by email) num_of_yrs
    from your_table t
    ) t where rn = 1;

通过电子邮件获得最长post_year组数年

2 个答案: