mysql怎么创建序列

CREATE TABLE users (
    id INT AUTO_INCREMENT PRIMARY KEY,
    name VARCHAR(50)
);

INSERT INTO users (name) VALUES ('Alice'), ('Bob');

SELECT * FROM users;

CREATE TABLE users (
    id INT,
    name VARCHAR(50),
    seq_no INT
);

DELIMITER //
CREATE TRIGGER before_user_insert
BEFORE INSERT ON users
FOR EACH ROW
BEGIN
    SET NEW.seq_no = (SELECT IFNULL(MAX(seq_no), 0) + 1 FROM users);
END;
//
DELIMITER ;

INSERT INTO users (name) VALUES ('Alice'), ('Bob');

SELECT * FROM users;

CREATE TABLE users (
    id INT AUTO_INCREMENT PRIMARY KEY,
    name VARCHAR(50),
    seq_no INT
);

DELIMITER //
CREATE PROCEDURE insert_user(IN p_name VARCHAR(50))
BEGIN
    DECLARE v_seq_no INT;
    SET v_seq_no = (SELECT IFNULL(MAX(seq_no), 0) + 1 FROM users);
    INSERT INTO users (name, seq_no) VALUES (p_name, v_seq_no);
END;
//
DELIMITER ;

CALL insert_user('Alice');
CALL insert_user('Bob');

SELECT * FROM users;