PostgreSQL with-delete"关系不存在"

Question

我正在使用postgreSQL 9.1,我想使用这个技巧从我的表中删除重复项:https: //stackoverflow.com/a/3822833/2239537

所以,我的查询看起来像这样:

WITH cte
 AS (SELECT ROW_NUMBER() 
 OVER (PARTITION BY code, card_id, parent_id 
     ORDER BY id DESC) RN
     FROM card)
DELETE FROM cte
WHERE RN > 1

但它告诉我

ERROR: relation "cte" does not exist
SQL state: 42P01
Character: 157

但是这个说法很好:

WITH cte
 AS (SELECT ROW_NUMBER() 
 OVER (PARTITION BY code, card_id, parent_id 
     ORDER BY id DESC) RN
     FROM merchantcard)
SELECT * FROM cte
WHERE RN > 1

任何想法如何让它工作？谢谢!

Answer 1

这是因为PostgreSQL中的CTE与SQL Server中的CTE不同.在SQL Server中,CTE就像一个可更新的视图,所以你可以从它们中删除或更新它们,在PostgreSQL中你不能.

你可以加入cte和delete,如:

with cte as (
    select
        id,
        row_number() over(partition by code, card_id, parent_id order by id desc) as rn
    from card
)
delete
from card
where id in (select id from cte where rn > 1)

另一方面,您可以在PostgreSQL中的CTE中编写DDL语句(参见文档),这可能非常方便.例如,您可以删除所有行card,然后仅插入具有row_number = 1的行:

with cte1 as (
    delete
    from card
    returning *
), cte2 as (
    select
        row_number() over(partition by code, card_id, parent_id order by id desc) as rn,
        *
    from cte1
)
insert into card
select <columns here>
from cte2
where rn = 1

Answer 2

我知道,你问的是如何使用WITH语句解决问题,并且已经得到了一个很好的答案.但我建议在你所链接的同一个问题中寻找替代方案.

这个如何？

DELETE FROM card
WHERE id NOT IN (
  SELECT MIN(id) FROM card
  GROUP BY code, card_id, parent_id 
);