MySQL 8.0查询根据下游内容在层次结构中的每个节点上递归计算大小

Question

这是在MySQL 8.0中。

我如何使用递归查询来自下而上地计算每个类别节点（类型= 1）的大小。

create table hierarchy (
    name     varchar(100),
    location varchar(100),
    type     int,
    size     int,
    parent_name varchar(100),
    parent_location varchar(100)
) engine=InnoDB default charset=UTF8MB4;

truncate hierarchy;
insert into hierarchy values
    ('music', '/', 1, 0, NULL, NULL),
    ('classical', '/music', 1, 0, 'music', '/'),
    ('pop', '/music', 1, 0, 'music', '/'),
    ('bonjovi', /music/pop', 'pop', '/music'),
    ('its_my_life.mp3', '/music/pop/bonjovi', 2, 4092, 'bonjovi', '/music/pop'),
    ('bach', '/music/classical', 1, 'classical', '/music'),
    ('flute_e_min.mp3', '/music/classical/bach', 2, 1024, 'bach', '/music/classical'),
    ('sonata_no1_g.mp3, '/music/classical/bach', 2, 2048, 'bach', '/music/classical'),  
select * from hierarchy;

[从层次结构中的给定节点开始，在本例中为音乐，我如何通过递归求和层次结构中（type = 2）的文件大小来获得每个直接后代类别组（type = 1）的大小？

name         location           parent_name   parent_location   total size
'music'      '/'                NULL          NULL              7164
'classical'  '/music'           'music'       '/'               3072
'pop'        '/music'           'music'       '/'               4092
'bonjovi'    '/music/pop'       'pop'         '/music'          4092
'bach'       '/music/classical' 'classical'   '/music'          3072
...

最初，类型= 1的节点具有默认值。该查询基于下游内容递归计算大小。

为您方便起见，提琴空间：https://www.db-fiddle.com/f/wozz4B6TEVmU95RPrQxvYd/0

Answer 1

您可以使用一对递归CTE解决此问题。第一个查找基于给定节点的所有类别（在本例中为music），第二个查找与每个类别关联的所有文件，并构建一个包含其大小的表，其中包含所有类别，直至根类别。然后将此表加入类别表，并在每个级别汇总文件大小：

WITH RECURSIVE categories AS (
  SELECT name, location, parent_name, parent_location, size
  FROM hierarchy
  WHERE name = 'music'
  UNION ALL
  SELECT h.name, h.location, h.parent_name, h.parent_location, h.size
  FROM hierarchy h
  JOIN categories c ON c.name = h.parent_name
  WHERE h.type = 1
),
filesizes AS (
  SELECT size, parent_name
  FROM hierarchy
  WHERE type = 2 AND parent_name IN (SELECT name FROM categories)
  UNION ALL
  SELECT f.size, h.parent_name
  FROM hierarchy h
  JOIN filesizes f ON f.parent_name = h.name
  WHERE h.parent_name IS NOT NULL
)
SELECT c.name, c.location, c.parent_name, c.parent_location,
       SUM(f.size) AS total_size
FROM categories c
JOIN filesizes f ON f.parent_name = c.name
GROUP BY c.name, c.location, c.parent_name, c.parent_location

输出：

name        location            parent_name     parent_location     total_size
music       /                   null            null                7164
classical   /music              music           /                   3072
pop         /music              music           /                   4092
bonjovi     /music/pop          pop             /music              4092
bach        /music/classical    classical       /music              3072

Demo on dbfiddle