mysql 数据库重复数据结构

CREATE TABLE users (
    id INT AUTO_INCREMENT PRIMARY KEY,
    username VARCHAR(255) UNIQUE,
    email VARCHAR(255) UNIQUE
);

CREATE TABLE users (
    user_id INT PRIMARY KEY,
    username VARCHAR(255),
    email VARCHAR(255)
);

DELETE t1 FROM users t1
INNER JOIN users t2 
WHERE t1.id > t2.id AND t1.username = t2.username;

CREATE VIEW unique_users AS
SELECT MIN(id) as id, username, email
FROM users
GROUP BY username, email;

DELIMITER //
CREATE PROCEDURE RemoveDuplicates()
BEGIN
    DECLARE done INT DEFAULT FALSE;
    DECLARE v_id INT;
    DECLARE v_username VARCHAR(255);
    DECLARE v_email VARCHAR(255);
    DECLARE cur CURSOR FOR SELECT id, username, email FROM users GROUP BY username, email HAVING COUNT(*) > 1;
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;

    OPEN cur;

    read_loop: LOOP
        FETCH cur INTO v_id, v_username, v_email;
        IF done THEN
            LEAVE read_loop;
        END IF;
        DELETE FROM users WHERE id <> v_id AND username = v_username AND email = v_email;
    END LOOP;

    CLOSE cur;
END //
DELIMITER ;