我有一个这样的mysql表
id Category parent
2 Garments 12
3 Gents Garments 2
4 Sarees 2
5 Bridal Sarees 4
6 IT 12
7 IT Hardware 6
8 IT Software 6
9 Web Design 8
10 Web Based Solution 8
11 E-Commerce Solution 9
12 root NULL
使用 mysql 查询
SELECT t1.category AS lev1, t2.category as lev2, t3.category as lev3,
t4.category as lev4
FROM categories AS t1
LEFT JOIN categories AS t2 ON t2.parent = t1.id
LEFT JOIN categories AS t3 ON t3.parent = t2.id
LEFT JOIN categories AS t4 ON t4.parent = t3.id
WHERE t1.category = 'root';
我能够得到这个结果
lev1 lev2 lev3 lev4
root Garments Gents Garments NULL
root Garments Sarees Bridal Sarees
root IT IT Hardware NULL
root IT IT Software Web Design
root IT IT Software Web Based Solution
现在我找不到在树状结构中的单个列中获取值的方法。例子
root
--Garments
----Gents Garments
----Sarees
--IT
----IT Hardware
----IT Software
------Web Design
------Web Based Solution
使用以下查询修改的问题：
我已经部分实现了上述结果，但钢材需要使用以下查询进行适当的分组
SELECT distinct t1.category AS category
FROM categories AS t1
LEFT JOIN categories AS t2 ON t2.parent = t1.id
LEFT JOIN categories AS t3 ON t3.parent = t2.id
LEFT JOIN categories AS t4 ON t4.parent = t3.id
WHERE t1.category = 'root'
union
SELECT distinct concat('--', t2.category) as category
FROM categories AS t1
LEFT JOIN categories AS t2 ON t2.parent = t1.id
LEFT JOIN categories AS t3 ON t3.parent = t2.id
LEFT JOIN categories AS t4 ON t4.parent = t3.id
WHERE t1.category = 'root'
union
SELECT distinct concat('----', t3.category) as category
FROM categories AS t1
LEFT JOIN categories AS t2 ON t2.parent = t1.id
LEFT JOIN categories AS t3 ON t3.parent = t2.id
LEFT JOIN categories AS t4 ON t4.parent = t3.id
WHERE t1.category = 'root'
union
SELECT distinct concat('------', t4.category) as category
FROM categories AS t1
LEFT JOIN categories AS t2 ON t2.parent = t1.id
LEFT JOIN categories AS t3 ON t3.parent = t2.id
LEFT JOIN categories AS t4 ON t4.parent = t3.id
WHERE t1.category = 'root'
我得到的结果是
root
--Garments
--IT
----Gents Garments
---- Sarees
----IT Hardware
----IT Software
------ Bridal Sarees
------Web设计
------基于Web的解决方案
但我想要像
root一样的结果
--Garments
----Gents Garments
---- Sarees
------ Bridal
Sarees --IT
----IT Hardware
-- --IT软件
------网页设计
------基于Web的解决方案