mysql通过单个查询获取结果父ID和类别ID？

Question

我有表，这样的价值观，

CREATE TABLE `category` (
`id` INT(4) NOT NULL AUTO_INCREMENT PRIMARY KEY , 
`category` VARCHAR(50) NOT NULL , 
`parent` INT(4) NOT NULL 
) 

INSERT INTO `category` VALUES (1, 'MCA', 9); 
INSERT INTO `category` VALUES (2, 'M Tech', 9); 
INSERT INTO `category` VALUES (3, 'B Tech', 9); 
INSERT INTO `category` VALUES (4, 'BioTech', 9); 
INSERT INTO `category` VALUES (5, 'InfoTech', 9); 
INSERT INTO `category` VALUES (6, 'Chemical', 10); 
INSERT INTO `category` VALUES (7, 'Indus', 10); 
INSERT INTO `category` VALUES (8, 'Physics', 10); 
INSERT INTO `category` VALUES (9, 'Information Science', 0); 
INSERT INTO `category` VALUES (10, 'Others Science', 0); 

我需要的类别和子类别方面获得的值的单个查询。第三个值为零，其他类别为子类别。

我需要输出为树状结构这样，

结果是：

Information Science 
    MCA 
    M Tech 
    B Tech 
    BioTech 
    InfoTech 
Others Science 
    Chemical 
    Indus 
    Physics 

Answer 1

也许这是你想要什么：

SELECT 
    T1.category AS category, 
    T2.category AS subcategory 
FROM category T1 
JOIN category T2 
ON T1.id = T2.parent 

 
category    subcategory 
'Information Science' 'MCA' 
'Information Science' 'M Tech' 
'Information Science' 'B Tech' 
'Information Science' 'BioTech' 
'Information Science' 'InfoTech' 
'Others Science'  'Chemical' 
'Others Science'  'Indus' 
'Others Science'  'Physics' 

这是假设只有你在你的层次结构中有两个层次。

Answer 2

Mysql有一个nice article for you。 虽然个人，我会去物化路径