Loopback:顺序过滤器中的MySQL函数

CREATE TABLE employees (
    id INT PRIMARY KEY,
    name VARCHAR(100),
    manager_id INT,
    FOREIGN KEY (manager_id) REFERENCES employees(id)
);

WITH RECURSIVE employee_hierarchy AS (
    SELECT id, name, manager_id
    FROM employees
    WHERE id = 5 -- 假设我们要查询ID为5的员工
    UNION ALL
    SELECT e.id, e.name, e.manager_id
    FROM employees e
    INNER JOIN employee_hierarchy eh ON e.id = eh.manager_id
)
SELECT * FROM employee_hierarchy;

DELIMITER //

CREATE PROCEDURE detect_cycle()
BEGIN
    DECLARE done INT DEFAULT FALSE;
    DECLARE current_id INT;
    DECLARE manager_id INT;
    DECLARE cur CURSOR FOR SELECT id, manager_id FROM employees;
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;

    OPEN cur;

    read_loop: LOOP
        FETCH cur INTO current_id, manager_id;
        IF done THEN
            LEAVE read_loop;
        END IF;

        -- 检测循环引用
        IF current_id = manager_id THEN
            SIGNAL SQLSTATE '45000'
                SET MESSAGE_TEXT = 'Cycle detected in employee hierarchy';
        END IF;
    END LOOP;

    CLOSE cur;
END //

DELIMITER ;

CALL detect_cycle();

DELIMITER //

CREATE PROCEDURE process_data_in_order()
BEGIN
    DECLARE done INT DEFAULT FALSE;
    DECLARE current_id INT;
    DECLARE cur CURSOR FOR SELECT id FROM data_table ORDER BY priority;
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;

    OPEN cur;

    read_loop: LOOP
        FETCH cur INTO current_id;
        IF done THEN
            LEAVE read_loop;
        END IF;

        -- 处理数据
        CALL process_single_data(current_id);
    END LOOP;

    CLOSE cur;
END //

DELIMITER ;

CALL process_data_in_order();