postgresql - 删除递归 child

Question

我有以下 sql 可以获取根论坛帖子的所有子孙。

with recursive all_posts (id, parentid, root_id) as
                (
                select t1.id,
                t1.parent_forum_post_id as parentid,
                t1.id as root_id
                from forumposts t1

                union all

                select c1.id,
                c1.parent_forum_post_id as parentid,
                p.root_id
                from forumposts
                c1
                join all_posts p on p.id = c1.parent_forum_post_id
                )

                select fp.id
                from forumposts fp inner join all_posts ap
                on fp.id=ap.id 
                where
                root_id=1349 
                group by fp.id

问题是我希望删除选定的记录。类似于 delete from forumposts fp where fp.id=(last select from the code above) 但这不起作用(我在“DELETE”处或附近收到语法错误)。这是我第一次使用递归，我一定遗漏了一些东西。感谢您的帮助。

Answer 1

您可以简单地使用 DELETE 语句而不是 SELECT 来完成您的工作:

with recursive all_posts (id, parentid, root_id) as (
    select t1.id,
    t1.parent_forum_post_id as parentid,
    t1.id as root_id
    from forumposts t1

    union all

    select c1.id,
    c1.parent_forum_post_id as parentid,
    p.root_id
    from forumposts
    c1
    join all_posts p on p.id = c1.parent_forum_post_id
)
DELETE FROM forumposts
 WHERE id IN (SELECT id FROM all_posts WHERE root_id=1349);

其他可能的组合，例如根据子表中已删除的行从主表中删除，check out the documentation .

编辑:对于 9.1 之前的 PostgresSQL 版本，您可以像这样使用初始查询:

DELETE FROM forumposts WHERE id IN (
    with recursive all_posts (id, parentid, root_id) as (
        select t1.id,
        t1.parent_forum_post_id as parentid,
        t1.id as root_id
        from forumposts t1

        union all

        select c1.id,
        c1.parent_forum_post_id as parentid,
        p.root_id
        from forumposts c1
        join all_posts p on p.id = c1.parent_forum_post_id
    )
    select id from all_posts ap where root_id=1349
);