使用mysql在nodejs中进行分页

Question

在我的项目中,我需要使用分页查询数据库,并根据当前搜索结果为用户提供查询功能.像限制一样,我无法找到任何与nodejs一起使用的东西.我的后端是mysql,我正在写一个休息API.

Answer 1

你可以试试这样的东西(假设你使用Express 4.x).

使用GET参数(此处页面是您想要的页面结果数,npp是每页的结果数).

在此示例中,查询结果results在响应有效负载的字段中设置,而分页元数据在pagination字段中设置.

至于根据当前搜索结果进行查询的可能性,您需要扩展一点,因为您的问题有点不清楚.

var express = require('express');
var mysql   = require('mysql');
var Promise = require('bluebird');
var bodyParser = require('body-parser');
var app = express();

var connection = mysql.createConnection({
  host     : 'localhost',
  user     : 'myuser',
  password : 'mypassword',
  database : 'wordpress_test'
});
var queryAsync = Promise.promisify(connection.query.bind(connection));
connection.connect();

// do something when app is closing
// see http://stackoverflow.com/questions/14031763/doing-a-cleanup-action-just-before-node-js-exits
process.stdin.resume()
process.on('exit', exitHandler.bind(null, { shutdownDb: true } ));

app.use(bodyParser.urlencoded({ extended: true }));

app.get('/', function (req, res) {
  var numRows;
  var queryPagination;
  var numPerPage = parseInt(req.query.npp, 10) || 1;
  var page = parseInt(req.query.page, 10) || 0;
  var numPages;
  var skip = page * numPerPage;
  // Here we compute the LIMIT parameter for MySQL query
  var limit = skip + ',' + numPerPage;
  queryAsync('SELECT count(*) as numRows FROM wp_posts')
  .then(function(results) {
    numRows = results[0].numRows;
    numPages = Math.ceil(numRows / numPerPage);
    console.log('number of pages:', numPages);
  })
  .then(() => queryAsync('SELECT * FROM wp_posts ORDER BY ID DESC LIMIT ' + limit))
  .then(function(results) {
    var responsePayload = {
      results: results
    };
    if (page < numPages) {
      responsePayload.pagination = {
        current: page,
        perPage: numPerPage,
        previous: page > 0 ? page - 1 : undefined,
        next: page < numPages - 1 ? page + 1 : undefined
      }
    }
    else responsePayload.pagination = {
      err: 'queried page ' + page + ' is >= to maximum page number ' + numPages
    }
    res.json(responsePayload);
  })
  .catch(function(err) {
    console.error(err);
    res.json({ err: err });
  });
});

app.listen(3000, function () {
  console.log('Example app listening on port 3000!');
});

function exitHandler(options, err) {
  if (options.shutdownDb) {
    console.log('shutdown mysql connection');
    connection.end();
  }
  if (err) console.log(err.stack);
  if (options.exit) process.exit();
}

这是package.json此示例的文件:

{
  "name": "stackoverflow-pagination",
  "dependencies": {
    "bluebird": "^3.3.3",
    "body-parser": "^1.15.0",
    "express": "^4.13.4",
    "mysql": "^2.10.2"
  }
}

Answer 2

我采用了@Benito的解决方案，并试图使其更清楚

var numPerPage = 20;
var skip = (page-1) * numPerPage; 
var limit = skip + ',' + numPerPage; // Here we compute the LIMIT parameter for MySQL query
sql.query('SELECT count(*) as numRows FROM users',function (err, rows, fields) {
    if(err) {
        console.log("error: ", err);
        result(err, null);
    }else{
        var numRows = rows[0].numRows;
        var numPages = Math.ceil(numRows / numPerPage);
        sql.query('SELECT * FROM users LIMIT ' + limit,function (err, rows, fields) {
            if(err) {
                console.log("error: ", err);
                result(err, null);
            }else{
                console.log(rows)
                result(null, rows,numPages);
            }
        });            
    }
});