删除递归子项

Question

我有以下sql让我所有的根forumpost的子孙.

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

我想要删除选中的记录.像从forumposts fp中删除的东西,其中fp.id =(最后从上面的代码中选择),但这不起作用(我在"DELETE"或附近得到语法错误).这是我第一次使用递归,我必须遗漏一些东西.任何帮助表示赞赏.

Answer 1

您只需使用该DELETE语句而不是SELECT完成工作:

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,请查看文档.

编辑:对于9.1之前的PostgresSQL版本,您可以使用这样的初始查询:

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
);