在MySQL中,可以使用递归公用表表达式(Recursive Common Table Expressions,简称CTE)来实现复杂查询中的递归排序
以下是一个使用MySQL递归排序的示例:
假设我们有一个组织结构表(organization),结构如下:
CREATE TABLE organization (
id INT AUTO_INCREMENT PRIMARY KEY,
name VARCHAR(255) NOT NULL,
parent_id INT DEFAULT NULL,
FOREIGN KEY (parent_id) REFERENCES organization(id)
);
表中数据如下:
INSERT INTO organization (name, parent_id) VALUES ('CEO', NULL);
INSERT INTO organization (name, parent_id) VALUES ('CTO', 1);
INSERT INTO organization (name, parent_id) VALUES ('CFO', 1);
INSERT INTO organization (name, parent_id) VALUES ('Dev Team', 2);
INSERT INTO organization (name, parent_id) VALUES ('HR Team', 2);
INSERT INTO organization (name, parent_id) VALUES ('Finance Team', 3);
现在,我们希望按照层级对组织结构进行排序,同一层级的成员按名称升序排列。可以使用以下递归查询实现:
WITH RECURSIVE org_hierarchy (id, name, parent_id, level, sort_order) AS (
SELECT id, name, parent_id, 1, COALESCE(parent_id, id)
FROM organization
WHERE parent_id IS NULL
UNION ALL
SELECT o.id, o.name, o.parent_id, oh.level + 1, COALESCE(o.parent_id, oh.sort_order)
FROM organization o
INNER JOIN org_hierarchy oh ON o.parent_id = oh.id
)
SELECT id, name, parent_id, level, sort_order
FROM org_hierarchy
ORDER BY level, sort_order;
查询结果如下:
+----+------------------+-----------+-------+-------------+
| id | name | parent_id | level | sort_order |
+----+------------------+-----------+-------+-------------+
| 1 | CEO | NULL | 1 | 1 |
| 2 | CTO | 1 | 2 | 2 |
| 3 | CFO | 1 | 2 | 3 |
| 4 | Dev Team | 2 | 3 | 1 |
| 5 | HR Team | 2 | 3 | 2 |
| 6 | Finance Team | 3 | 3 | 1 |
+----+------------------+-----------+-------+-------------+
在这个示例中,我们首先使用递归CTE创建了一个名为org_hierarchy
的临时表,其中包含了每个组织成员的ID、名称、父ID、层级和排序顺序。然后,我们对这个临时表进行排序,先按层级排序,再按排序顺序排序。最后,我们得到了按照层级和名称升序排列的组织结构。