仅在窗口分区中查找值不重复的行。

Question

我想看看为什么某些descriptions对于相同的permit id是不同的。这是桌子(我用的是雪花)：

create or replace table permits (permit varchar(255), description varchar(255));

// dupe permits, dupe descriptions, throw out
INSERT INTO permits VALUES ('1', 'abc'); 
INSERT INTO permits VALUES ('1', 'abc');

// dupe permits, unique descriptions, keep
INSERT INTO permits VALUES ('2', 'def1'); 
INSERT INTO permits VALUES ('2', 'def2');
INSERT INTO permits VALUES ('2', 'def3');

// dupe permits, unique descriptions, keep
INSERT INTO permits VALUES ('3', NULL);   
INSERT INTO permits VALUES ('3', 'ghi1');

// unique permit, throw out
INSERT INTO permits VALUES ('5', 'xyz'); 

我想要的是查询这个表，只获取具有重复I但有不同描述的行集。

我想要的输出是：

+---------+-------------+
| PERMIT  | DESCRIPTION |
+---------+-------------+
|       2 | def1        |
|       2 | def2        |
|       2 | def3        |
|       3 |             |
|       3 | ghi1        |
+---------+-------------+

我试过这个：

with with_dupe_counts as (
    select
        count(permit) over (partition by permit order by permit) as permit_dupecount,
        count(description) over (partition by permit order by permit) as description_dupecount,
        permit,
        description
    from permits
)
select *
from with_dupe_counts
where permit_dupecount > 1 
and description_dupecount > 1

这给了我许可1和2，并计算了它们是否是唯一的描述：

+------------------+-----------------------+--------+-------------+
| PERMIT_DUPECOUNT | DESCRIPTION_DUPECOUNT | PERMIT | DESCRIPTION |
+------------------+-----------------------+--------+-------------+
|                2 |                     2 |      1 | abc         |
|                2 |                     2 |      1 | abc         |
|                3 |                     3 |      2 | def1        |
|                3 |                     3 |      2 | def2        |
|                3 |                     3 |      2 | def3        |
+------------------+-----------------------+--------+-------------+

我认为会有用的是

count(unique description) over (partition by permit order by permit) as description_dupecount

但正如我所意识到的，有很多东西在窗口函数中不起作用。这个问题不一定是“如何使计数(唯一x)在窗口函数中工作”，因为我不知道这是否是解决这个问题的最佳方法。

我认为一个简单的group by将无法工作，因为我想要返回原始行。

Answer 1

一种方法是使用min()、max()和count()。

select *
from (select p.*,
             min(description) over (partition by permit) as min_d,
             max(description) over (partition by permit) as max_d,
             count(description) over (partition by permit) as cnt_d,
             count(*) over (partition by permit) as cnt,
            count(permit) over (partition by permit order by permit) as permit_dupecount
      from permits
     )
where min_d <> max_d or cnt_d <> cnt;

Answer 2

我只会用exists

select p.*
from permits p
where exists (
    select 1 
    from permits p1 
    where p1.permit = p.permit and p1.description <> p.description
)

要处理null值，我们可以使用标准的空安全相等操作符IS DISTINCT FROM，它支持：

select p.*
from permits p
where exists (
    select 1 
    from permits p1 
    where 
        p1.permit = p.permit 
        and p1.description is distinct from p.description
)

Answer 3

应起作用

SELECT DISTINCT p1.permit, p1.description
FROM permits p1
JOIN permits p2 ON p1.permit = p2.permit
WHERE p1.description != p2.description OR p1.description IS NULL AND p2.description IS NOT NULL