mysql数据库怎么创建序列

CREATE TABLE my_table (
  id INT AUTO_INCREMENT PRIMARY KEY,
  column1 VARCHAR(255),
  column2 INT
);

DELIMITER $$
CREATE TRIGGER trigger_name
BEFORE INSERT ON my_table
FOR EACH ROW
BEGIN
  DECLARE next_id INT;
  SET next_id = (
    SELECT IFNULL(MAX(column2), 0) + 1
    FROM my_table
  );
  SET NEW.column2 = next_id;
END$$
DELIMITER ;

INSERT INTO my_table (column1) VALUES ('Value 1');
INSERT INTO my_table (column1) VALUES ('Value 2');
INSERT INTO my_table (column1) VALUES ('Value 3');