如何在SQLite中获取分层树路径？

Question

想象一个定义树结构的简单表。

create table nodes (
    id integer primary key,
    name text not null,
    parent integer
)

一些示例节点：

节点1是2的父级，而节点3是4的父级。是否可以在SQLite中编写SQL查询，使其返回：

id    path
1     foo
2     foo/bar
3     foo/baz
4     foo/baz/stuff

Answer 1

您可以使用recursive common table expressions在SQLite中执行递归。

将返回节点路径的示例查询：

with recursive paths(id, name, path) as (
    select id, name, name from nodes where parent is null
    union
    select nodes.id, nodes.name, paths.path || '/' || nodes.name
    from nodes join paths where nodes.parent = paths.id
)
select id, path from paths