mysql语句实现循环

WITH RECURSIVE department_hierarchy AS (
    -- 初始查询：选择根部门（没有上级部门的部门）
    SELECT id, name, parent_id, 1 AS level
    FROM departments
    WHERE parent_id IS NULL

    UNION ALL

    -- 递归查询：选择每个部门的子部门，并增加层级
    SELECT d.id, d.name, d.parent_id, dh.level + 1
    FROM departments d
    INNER JOIN department_hierarchy dh ON d.parent_id = dh.id
)
SELECT * FROM department_hierarchy;

DELIMITER //

CREATE PROCEDURE InsertNumbers()
BEGIN
    DECLARE i INT DEFAULT 1;
    WHILE i <= 10 DO
        INSERT INTO numbers (value) VALUES (i);
        SET i = i + 1;
    END WHILE;
END //

DELIMITER ;

CALL InsertNumbers();

CREATE TEMPORARY TABLE temp_orders AS
SELECT id, order_date
FROM orders;

SELECT o1.id, o1.order_date, o2.id AS next_order_id, o2.order_date AS next_order_date
FROM temp_orders o1
LEFT JOIN temp_orders o2 ON o1.id < o2.id
ORDER BY o1.order_date, o2.order_date;