mysql嵌套游标

DELIMITER //

CREATE PROCEDURE NestedCursorExample()
BEGIN
    DECLARE done INT DEFAULT FALSE;
    DECLARE v_id INT;
    DECLARE v_name VARCHAR(255);
    DECLARE cur1 CURSOR FOR SELECT id, name FROM table1;
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;

    OPEN cur1;

    read_loop: LOOP
        FETCH cur1 INTO v_id, v_name;
        IF done THEN
            LEAVE read_loop;
        END IF;

        -- 嵌套游标示例
        DECLARE v_sub_id INT;
        DECLARE v_sub_name VARCHAR(255);
        DECLARE cur2 CURSOR FOR SELECT sub_id, sub_name FROM table2 WHERE parent_id = v_id;
        DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;

        OPEN cur2;

        sub_read_loop: LOOP
            FETCH cur2 INTO v_sub_id, v_sub_name;
            IF done THEN
                LEAVE sub_read_loop;
            END IF;

            -- 处理嵌套游标数据
            SELECT CONCAT(v_name, ' - ', v_sub_name) AS combined_name;

        END LOOP sub_read_loop;

        CLOSE cur2;
    END LOOP read_loop;

    CLOSE cur1;
END //

DELIMITER ;