nodejs mysql 实现分页的方法

var express = require('express');
var router = express.Router();
var settings = require('../settings.js');
var mysql = require('mysql2');

router.get('/', function(req, res, next) {
  var current_page = 1; //默认为1
  var num = 9; //一页条数
  if (req.query.page) {
    current_page = parseInt(req.query.page);
  }

  var last_page = current_page - 1;
  if (current_page <= 1) {
    last_page = 1;
  }
  var next_page = current_page + 1;
  var str = 'SELECT left(paragraph,50) as paragraph,date,id FROM notice limit ' + num + ' offset ' + num * (current_page - 1);
  var conn = mysql.createConnection(settings.db);

  conn.connect();
  conn.query(str, function(err, rows, fields) {
    if (err) {
      req.flash('error', '数据查询有误');
    }
    if (!err) {
      if (!rows[0]) {
        req.flash('error', '已到最后一页,请返回');
      }
      res.render('notice', {
        last_page: last_page,
        next_page: next_page,
        current_page: current_page,
        mes: rows,
        error: req.flash('error').toString()
      });

    }
  });
  conn.end();
});

module.exports = router;