mysql WITH RECURSIVE语法的具体使用

WITH RECURSIVE cte_name (column1, column2, ...) AS (
  -- 非递归的初始部分，定义了 CTE 的起点
  SELECT ...
  FROM ...

  UNION ALL

  -- 递归部分，可以引用 CTE 的别名
  SELECT ...
  FROM cte_name
  WHERE ...
)
-- 最后的 SELECT 或其他 DML 语句，使用递归 CTE
SELECT * FROM cte_name;

WITH RECURSIVE employee_hierarchy (id, name, manager_id, path) AS (
  -- 非递归的初始部分：查找顶层经理（没有经理的员工）
  SELECT
    id,
    name,
    manager_id,
    CONCAT(name, '/') AS path -- 使用 CONCAT 创建初始路径
  FROM employees
  WHERE manager_id IS NULL
  
  UNION ALL
  
  -- 递归部分：查找所有下属
  SELECT
    e.id,
    e.name,
    e.manager_id,
    CONCAT(e.name, '/', eh.path) AS path -- 将当前员工添加到路径中
  FROM employees e
  INNER JOIN employee_hierarchy eh ON e.manager_id = eh.id
)
SELECT * FROM employee_hierarchy;

CREATE TABLE rkk_dzblzdl (
id int NOT NULL AUTO_INCREMENT COMMENT ‘id',
month varchar(10) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci DEFAULT NULL COMMENT ‘月份(1-12月)',
zdcs int DEFAULT NULL COMMENT ‘诊断次数',
xzqh varchar(12) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci DEFAULT NULL COMMENT ‘行政区划',
PRIMARY KEY (id)
)COMMENT=‘电子病历诊断量';

WITH RECURSIVE RecentMonths AS (  
    SELECT DATE_FORMAT(CURDATE(), '%Y-%m') AS month  
    UNION ALL  
    SELECT DATE_FORMAT(DATE_SUB(STR_TO_DATE(CONCAT(month, '-01'), '%Y-%m-%d'), INTERVAL 1 MONTH), '%Y-%m')  
    FROM RecentMonths  
    WHERE STR_TO_DATE(CONCAT(month, '-01'), '%Y-%m-%d') > DATE_SUB(CURDATE(), INTERVAL 12 MONTH)  
)  
  
SELECT   
    COALESCE(r.xzqh, rm.month) AS xzqh,   
    rm.month AS month,   
    SUM(r.zdcs) AS zdcs_count,  
    (SELECT MAX(month) FROM rkk_dzblzdl) AS last_updated_month_in_table  
FROM   
    RecentMonths rm  
LEFT JOIN   
    rkk_dzblzdl r ON rm.month = r.month  
GROUP BY   
    rm.month, r.xzqh  
ORDER BY   
    STR_TO_DATE(CONCAT(rm.month, '-01'), '%Y-%m-%d') DESC, r.xzqh;