一篇文章学会SQL中的递归用法(Mysql)

WITH RECURSIVE recursive_query_name (col1, col2, ..., coln) AS (
    -- 递归部分
    SELECT 
			initial_query_result_col1, 
			initial_query_result_col2, 
			...,
			initial_query_result_coln
    FROM initial_query
    UNION ALL
    SELECT 
			recursive_query_result_col1,
			recursive_query_result_col2, 
			..., 
			recursive_query_result_coln
    FROM recursive_query_name, recursive_query
    WHERE recursive_query_condition
)
-- 终止条件部分
SELECT * FROM recursive_query_name WHERE termination_condition;

CREATE TABLE company_department (
    department_id INT PRIMARY KEY,
    department_name VARCHAR(50),
    parent_department_id INT REFERENCES company_department(department_id)
);

INSERT INTO company_department 
    (department_id, department_name, parent_department_id)
VALUES
    (1, '公司', NULL),
    (2, '人力资源部', 1),
    (3, '财务部', 1),
    (4, '市场部', 1),
    (5, '技术部', 1),
    (6, '招聘部', 2),
    (7, '薪资部', 2),
    (8, '成本控制部', 3),
    (9, '收支管理部', 3),
    (10, '品牌推广部', 4),
    (11, '销售部', 4),
    (12, '前端开发部', 5),
    (13, '后端开发部', 5)

WITH RECURSIVE department_tree (department_id, department_name, parent_department_id, depth, path) AS (
		SELECT 
			department_id, 
			department_name, 
			parent_department_id, 
			1 AS depth, 
			CAST(department_id AS CHAR(200)) AS path
		FROM company_department
		WHERE parent_department_id IS NULL
		UNION ALL
		SELECT 
			cd.department_id, 
			cd.department_name, 
			cd.parent_department_id, 
			dt.depth + 1 AS depth, 
			CONCAT(dt.path, ',', cd.department_id) AS path
		FROM company_department cd
			JOIN department_tree dt ON cd.parent_department_id = dt.department_id
	)
SELECT 
	department_id, department_name, parent_department_id, depth, path
FROM department_tree
ORDER BY path;