我有一个master_data
,其中包含所有类型的数据,例如Learning
、Program
和Course
。另一个表 mapping
告诉您父/子关系。
这里是分组/继承
学习 -> 程序 -> 类(class)
A Learning may have multiple Programs, a Program may have multiple Courses. Also, a Program can be part of multiple Learnings and a Course can be part of multiple Programs.
如何通过保留一个额外的列来引入数据,例如 parent
来标识父级,以便它有助于对行进行分组。
主数据
id title description type
----------------------------------------------------------------
1 How to Present some info Learning
2 Securing Data more info Learning
3 Preparation plan more info Program
4 Protecting System info Program
5 Presentation mediums some info Program
6 know the importance some info Course
7 Notice the key concepts some info Course
8 Presenting in PPT some info Course
9 Presenting in Video format some info Course
10 Update the System some info Course
11 Chose a Strong password some info Course
映射
id learning_id program_id course_id
---------------- ----------- --------------
1 1 3 6
2 1 5 6
3 1 3 7
4 1 5 8
5 1 5 9
6 2 4 6
7 2 4 10
8 2 4 11
结果
id title description type parent
-------------------------------------------------------------------------
1 How to Present some info Learning 1 (itself)
3 Preparation plan more info Program 1
5 Presentation mediums some info Program 1
6 know the importance some info Course 3
7 Notice the key concepts some info Course 3
8 Presenting in PPT some info Course 5
9 Presenting in Video format some info Course 5
这里,程序 3,5 是学习 1 的一部分。类(class) 6,7 属于程序 3,类(class) 8,9 属于程序 5
Mysql中上述查询
CREATE TABLE `master_data` (
`id` INT NOT NULL AUTO_INCREMENT,
`title` VARCHAR(255) NOT NULL,
`description` TEXT NOT NULL,
`type` VARCHAR(45) NOT NULL,
PRIMARY KEY (`id`));
INSERT INTO `master_data` (`id`, `title`, `description`, `type`) VALUES
('1', 'How to Present', 'some info', 'Learning'),
('2', 'Securing Data', 'few more info', 'Learning'),
('3', 'Preparation plan', 'informatoin abt this', 'Program'),
('4', 'Protecting System', 'security info', 'Program'),
('5', 'Presentation mediums', 'some info', 'Program'),
('6', 'You should know the importance', 'some info', 'Course'),
('7', 'Notice the key concepts', 'some info', 'Course'),
('8', 'Presenting in PPT', 'some info', 'Course'),
('9', 'Presenting in Vedio format', 'some info', 'Course'),
('10', 'Update the System', 'some info', 'Course'),
('11', 'Chose a Strong password', 'some info', 'Course');
CREATE TABLE `mapping` (
`id` INT NOT NULL AUTO_INCREMENT,
`learning_id` INT NOT NULL,
`program_id` INT NOT NULL,
`course_id` INT NOT NULL,
PRIMARY KEY (`id`));
INSERT INTO `mapping` (`id`, `learning_id`, `program_id`, `course_id`) VALUES
('1', '1', '3', '6'),
('2', '1', '5', '6'),
('3', '1', '3', '7'),
('4', '1', '5', '8'),
('5', '1', '5', '9'),
('6', '2', '4', '6'),
('7', '2', '4', '10'),
('8', '2', '4', '11');
最佳答案
你也可以在 UNION 子句的帮助下完成:
select id,title,description,type,id from master_data where type='Learning'
UNION
select program_id,title,description,type,learning_id from master_data md, mapping m where md.id=m.program_id
UNION
select course_id,title,description,type,program_id from master_data md, mapping m where md.id=m.course_id;
为了数据的准确性和良好的性能,您应该有适当的约束和索引。
关于mysql - 如何使用映射表将表行映射到多个父行?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/47901177/