Hibernate: Encountered a duplicated sql alias [] during auto-discovery of a native-sq

StringBuffer sql = new StringBuffer();
        sql.append("SELECT a.id,a.teacher_name,a.user_code,r.id AS competitionId,r.competition_name,t.group_id,t.group_name");
        sql.append(" FROM app_teacher a");
        sql.append("  LEFT JOIN competition_record_teacher t");
        sql.append("  ON a.user_code = t.mobile");
        sql.append("  LEFT JOIN competition_record r");
        sql.append("     ON t.competition_id = r.id");
        sql.append(" WHERE r.status = 0 AND a.user_code=?");
        Query query =  session().createSQLQuery(sql.toString());