SQLite到Postgres层次结构查询

Question

下面是我在SQLite中成功使用的一个查询。它创建了属于"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; 

我试图对其进行修改，使其与Postgres一起工作，但我说“深度”是一种矛盾的说法是错误的。

有两个简单的表：

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

所有列都是整数，但*_name是varchars。

有谁可以帮我？

Answer 1

我认为您需要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select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;