关于sql拼接的知识点 where1=1

public int findTotalCount(int cid,String rname) {
    //String sql="select count(*) from tab_route where cid=?";// cid就是每个旅游类别的标记比如 cid=1 代表休闲类那么多有休闲都会被查询出来
    String sql="select count(*) from tab_route where 1 = 1 ";
    StringBuilder sb=new StringBuilder(sql);
    List params=new ArrayList();//所有条件
    //判断参数是否有值
    if (cid !=0){//没有参数那么拼接的就是"select count(*) from tab_route where 1 = 1 "
        sb.append(" and cid = ? ");//添加?对应的值
        params.add(cid);
    }if (rname !=null && rname.length()>0){
        sb.append(" and rname like ? ");
        params.add("%"+rname+"%");
    }
    sql = sb.toString();
    System.out.println(sql);
    return template.queryForObject(sql,Integer.class,params.toArray());//返回一个整数
}