如何从父子关系中的单个表中获取全家ID

Question

我有一个MySQL表（系列），如下所示

id parent_id 
4   null
5   4 
6   null 
7   null
36  5 
37  6 

这时我传递

id as 4 it should return 4 -5 - 36 
id as 5 it should return 4 -5 - 36 
id as 6 it should return 6 - 37 
id as 7 it should return 7
id as 36 it should return 4 -5 - 36 
id as 37 it should return 37 - 6 

SELECT t1.id AS lev1, t2.id as lev2, t3.id as lev3, t4.id as lev4
FROM family AS t1
LEFT JOIN family AS t2 ON t2.parent_id = t1.id
LEFT JOIN family AS t3 ON t3.parent_id = t2.id
LEFT JOIN family AS t4 ON t4.parent_id = t3.id
WHERE t1.id =5; 

但是这些代码在某些情况下失败了。有人可以帮我这个吗？

Answer 1

根据提供的内容，我可以看到36和37不会返回您期望的值。

t1.id = 36

然后

t2.parent_id应该= 36，但它们都没有。

此外，＆＃39;失败＆＃39;是不是很模糊是否有错误或者你得到的结果与你预期的不同？如果是后者，那么你可能会期待错误的结果。