SQLite 到 Postgres 层次结构查询

Question

这是我在 SQLite 中成功使用的查询。它创建属于“Pak”的所有链接的层次结构。

WITH LinkTree(link_id, link_pid, pak_id, link_name, depth)
AS
(
SELECT *, 0 AS depth FROM links
WHERE link_pid = 0

UNION ALL
SELECT l.*, lt.depth+1 AS depth FROM LinkTree lt
JOIN links l ON (lt.link_id = l.link_pid)
)
SELECT * FROM LinkTree WHERE pak_id = 1; 

我正在尝试修改它以使其与 Postgres 一起使用，但我收到一条错误消息，指出“深度”不明确。

使用了两个简单的表:

Paks: pak_id, pak_name
Links: link_id, link_pid, link_name, pak_id

所有列都是整数，除了 *_name 是 varchars。

谁能帮帮我？

Answer 1

我认为你需要 RECURSIVE 关键字:

WITH RECURSIVE LinkTree(link_id, link_pid, pak_id, link_name, depth)
AS
(
SELECT *, 0 AS depth FROM links
WHERE link_pid = 0

UNION ALL
SELECT l.*, lt.depth+1 AS depth FROM LinkTree lt
JOIN links l ON (lt.link_id = l.link_pid)
)
SELECT * FROM LinkTree WHERE pak_id = 1; 

编辑:

不要在选择中使用*:

WITH LinkTree(link_id, link_pid, pak_id, link_name, depth)
AS
(
  SELECT link_id, link_pid, pak_id, link_name, 0 AS depth 
  FROM links
  WHERE link_pid = 0
  UNION ALL
  SELECT l.link_id, l.link_pid, l.pak_id, l.link_name, lt.depth+1 AS depth 
  FROM LinkTree lt
  JOIN links l 
    ON lt.link_id = l.link_pid
)
SELECT * 
FROM LinkTree 
WHERE pak_id = 1;