根据层次结构显示数据[祖父->父->子]

Question

嗨，我想将数据显示为如下图所示的层次结构方式

这是我的数据库表结构

这是我使用的查询，但它不是我想要的完美结果

SELECT 

t1.parent_id AS primary_Id,
t2.parent_id AS secondary_Id,
t3.parent_id AS teritiary_Id

FROM ucode AS t1
LEFT JOIN ucode AS t2 ON t2.parent_id = t1.id
LEFT JOIN ucode AS t3 ON t3.parent_id = t2.parent_id

输出是

这不是我需要的

还有一种我尝试过的方法

SELECT 
    
    t1.parent_id AS primary_Id,
    t2.parent_id AS secondary_Id,
    t3.parent_id AS teritiary_Id
    
    FROM ucode AS t1
    LEFT JOIN ucode AS t2 ON t2.parent_id = t1.id
    LEFT JOIN ucode AS t3 ON t3.parent_id = t2.id

输出是

你能给我正确的解决方案吗..

Answer 1

这里是查询

Select gparent, parent, id from ucode as c_tbl,
(SELECT gparent, id as parent from ucode as p_tbl,
(SELECT id as gparent FROM `ucode` WHERE parent_id = 0) as gp_tbl
where p_tbl.parent_id = gp_tbl.gparent) parent_tbl
where c_tbl.parent_id = parent_tbl.parent;

点击Demo查看结果

Answer 2

您需要使用 INNER JOIN 而不是 LEFT JOIN 并将查询限制为仅返回有孩子的父母使用 WHERE

我的查询不会像您想要显示的那样跳过列值，但您可以在循环以下查询结果时使用 PHP。

SELECT 
    t1.parent_id AS primary_Id,
    t2.parent_id AS secondary_Id,
    t3.parent_id AS teritiary_Id
FROM ucode AS t1
INNER JOIN ucode AS t2 ON (t2.parent_id = t1.id )
INNER JOIN ucode AS t3 ON (t3.parent_id = t2.id )
where t1.parent_id = 0

Demo