sql - PostgreSQL with-delete "relation does not exists"

Question

我正在使用 postgreSQL 9.1，我想使用这个提示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

但是这个语句工作正常:

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

有什么想法可以让它发挥作用吗？谢谢!

Answer 1

那是因为 PostgreSQL 中的 CTE 与 SQL Server 中的 CTE 工作方式不同。在 SQL Server 中，CTE 就像一个可更新的 View ，因此您可以从中删除或更新它们，在 PostgreSQL 中则不能。

你可以加入cte和删除，比如:

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 的 CTE 中编写 DDL 语句(参见 documentation)，这可能非常方便。例如，您可以删除 card 中的所有行，然后仅插入 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