如何获得子树表在PHP

Question

我有这样的一个表：

id title  parent_id 
1  A   0 
2  B   0 
3  C   1 
4  F   3 
5  O   3 
6  D   2 
7  J   6 
8  T   2 
9  P   8 


A 
    C 
     F 
     O 

B 
    D 
    J 
    T 
    P 

现在，如果我给2，这个功能应该返回：

6 
8 
7 
9 

而且，如果我给3它函数返回：

4 
5 

• 我不想只是叶子节点！
• 我认为有一个SQL查询。

Answer 1

只是SQL：

select id, 
     title, 
     parent_id 
from (select * from products 
     order by parent_id, id) base, 
     (select @pv := '3') tmp 
where find_in_set(parent_id, @pv) > 0 
and  @pv := concat(@pv, ',', id) 

Answer 2

我认为你需要与自己连接表。我没有自己尝试，但它是像下面的代码

SELECT a.id, a.title 
FROM tbl AS a 
WHERE a.id = :id 

UNION 

SELECT b.id, b.title 
FROM tbl AS a 
INNER JOIN tbl AS b ON a.id = b.parent_id 
WHERE a.id = :id 

UNION 

SELECT c.id, c.title 
FROM tbl AS a 
INNER JOIN tbl AS b ON a.id = b.parent_id 
INNER JOIN tbl AS c ON b.id = c.parent_id 
WHERE a.id = :id 

UNION 

SELECT d.id, d.title 
FROM tbl AS a 
INNER JOIN tbl AS b ON a.id = b.parent_id 
INNER JOIN tbl AS c ON b.id = c.parent_id 
INNER JOIN tbl AS d ON c.id = d.parent_id 
WHERE a.id = :id 

... 

继续添加查询，直到你需要的深度数。还有其他方法，例如使用存储过程。