sql语句实现分页技术

select user_id, user_name, password, contact_tel, email, create_date
from(
select rownum rn, user_id, user_name, password, contact_tel, email, create_date
from
(
select user_id, user_name, password, contact_tel, email, create_date from t_user where user_id <> 'root' order by user_id
) where rownum <= 4
) where rn > 1

/**
* 分页查询
* @param pageNo  第几页
* @param pageSize  每页多少条数据
* @return pageModel
*/
public PageModel<User> findUserList(int pageNo, int pageSize){
StringBuffer sbSql = new StringBuffer();
sbSql.append("select user_id, user_name, password, contact_tel, email, create_date ")
.append("from ")
.append("( ")
.append("select rownum rn, user_id, user_name, password, contact_tel, email, create_date ")
.append("from ")
.append("( ")
.append("select user_id, user_name, password, contact_tel, email, create_date from t_user where user_id <> 'root' order by user_id ")
.append(") where rownum <= ? ")
.append(") where rn > ? ");
Connection conn = null;
PreparedStatement pstmt = null;
ResultSet rs = null;
PageModel<User> pageModel = null;
try{
conn = DbUtil.getConnection();
pstmt = conn.prepareStatement(sbSql.toString());
pstmt.setInt(1, pageNo * pageSize);
pstmt.setInt(2, (pageNo - 1) * pageSize);
rs = pstmt.executeQuery();
List<User> userList = new ArrayList<User>();
while (rs.next()){
User user = new User();
user.setUserId(rs.getString("user_id"));
user.setUserName(rs.getString("user_name"));
user.setPassword(rs.getString("password"));
user.setContactTel(rs.getString("contact_tel"));
user.setEmail(rs.getString("email"));
user.setCreateDate(rs.getTimestamp("create_date"));
userList.add(user);
}
pageModel = new PageModel<User>();
pageModel.setList(userList);
pageModel.setTotalRecords(getTotalRecords(conn));
pageModel.setPageSize(pageSize);
pageModel.setPageNo(pageNo);
}catch(SQLException e){
e.printStackTrace();
}finally{
DbUtil.close(rs);
DbUtil.close(pstmt);
DbUtil.close(conn);
}
return pageModel;
}