MySQL 9.0 Release Notes
        
ALTER PROCEDURE proc_name [characteristic ...]
characteristic: {
    COMMENT 'string'
  | LANGUAGE SQL
  | { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA }
  | SQL SECURITY { DEFINER | INVOKER }
}
      This statement can be used to change the characteristics of a
      stored procedure. More than one change may be specified in an
      ALTER PROCEDURE statement. However,
      you cannot change the parameters or body of a stored procedure
      using this statement; to make such changes, you must drop and
      re-create the procedure using DROP
      PROCEDURE and CREATE
      PROCEDURE.
    
      You must have the ALTER ROUTINE
      privilege for the procedure. By default, that privilege is granted
      automatically to the procedure creator. This behavior can be
      changed by disabling the
      automatic_sp_privileges system
      variable. See Section 27.2.2, “Stored Routines and MySQL Privileges”.