mysql 游标中嵌套游标

DELIMITER //

CREATE PROCEDURE NestedCursorExample()
BEGIN
    DECLARE v_customer_id INT;
    DECLARE v_customer_name VARCHAR(255);
    DECLARE done INT DEFAULT FALSE;

    -- 声明外部游标
    DECLARE cur_orders CURSOR FOR
        SELECT customer_id FROM orders;

    -- 声明内部游标
    DECLARE cur_customers CURSOR FOR
        SELECT id, name FROM customers;

    -- 声明继续处理标志
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;

    OPEN cur_orders;

    read_loop: LOOP
        FETCH cur_orders INTO v_customer_id;
        IF done THEN
            LEAVE read_loop;
        END IF;

        OPEN cur_customers;
        customer_loop: LOOP
            FETCH cur_customers INTO v_customer_id, v_customer_name;
            IF done THEN
                LEAVE customer_loop;
            END IF;

            -- 处理嵌套游标的数据
            SELECT v_customer_id, v_customer_name;
        END LOOP customer_loop;
        CLOSE cur_customers;
    END LOOP read_loop;

    CLOSE cur_orders;
END //

DELIMITER ;

CALL NestedCursorExample();