mysql 嵌套游标

DELIMITER //

CREATE PROCEDURE NestedCursorExample()
BEGIN
    DECLARE outer_cursor CURSOR FOR SELECT id, name FROM users;
    DECLARE inner_cursor CURSOR FOR SELECT id, email FROM user_details;
    DECLARE done INT DEFAULT FALSE;
    DECLARE outer_id INT;
    DECLARE outer_name VARCHAR(255);
    DECLARE inner_id INT;
    DECLARE inner_email VARCHAR(255);

    OPEN outer_cursor;

    read_outer_loop: LOOP
        FETCH outer_cursor INTO outer_id, outer_name;
        IF done THEN
            LEAVE read_outer_loop;
        END IF;

        OPEN inner_cursor;
        read_inner_loop: LOOP
            FETCH inner_cursor INTO inner_id, inner_email;
            IF done THEN
                LEAVE read_inner_loop;
            END IF;

            -- 处理嵌套游标的数据
            SELECT CONCAT('User ID: ', outer_id, ', Name: ', outer_name, ', Email: ', inner_email);

        END LOOP read_inner_loop;
        CLOSE inner_cursor;
    END LOOP read_outer_loop;
    CLOSE outer_cursor;
END //

DELIMITER ;

CALL NestedCursorExample();