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，并为用户提供基于当前搜索结果进行查询的功能。像限制之类的东西，我找不到任何与nodejs一起使用的东西。我的后端是mysql，我正在写一个rest api。

Answer 1

我采用了@Benito的解决方案，并试图使其更清晰

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);
            }
        });            
    }
});

Answer 2

您可以尝试类似的方法（假设您使用Express 4.x）。

使用GET参数（这里page是你想要的页面结果数，npp是每页结果数）。

在此示例中，查询结果设置在响应负载的results 字段中，而分页元数据设置在pagination 字段中。

至于是否可以根据当前搜索结果进行查询，您需要稍微扩展一下，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();
}

这是此示例的 package.json 文件：

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

Answer 3

正在寻找快速解决方案。也许对某人有用。

SELECT id  FROM complexCoding LIMIT ? OFFSET ?
",req.query.perpage,((req.query.page-1) * req.query.perpage)

别忘了按照total count of id除以perpage来分页

Answer 4

我写了一个分页类，以便在不同的页面上使用它，我使用引导程序来设置链接样式，如果你不使用引导程序，你可以更改它。

物品路线

router.get('/items/:page',(req,res) => {
const db = require('mysql'),
        Pagination = require('./pagination'),

        // Get current page from url (request parameter)
        page_id = parseInt(req.params.page),
        currentPage = page_id > 0 ? page_id : currentPage,

//Change pageUri to your page url without the 'page' query string 
        pageUri = '/items/';

        /*Get total items*/
        db.query('SELECT COUNT(id) as totalCount FROM items',(err,result)=>{

            // Display 10 items per page
            const perPage = 10,
                totalCount = result[0].totalCount;

            // Instantiate Pagination class
            const Paginate = new Pagination(totalCount,currentPage,pageUri,perPage);


            /*Query items*/
            db.query('SELECT * FROM items LIMIT '+Paginate.perPage+' OFFSET '+Paginate.start,(err,result)=>{

                data = {
                    items : result,
                    pages : Paginate.links()
                }

                // Send data to view
                res.render('items',data);
            });
        });

});

在项目视图中，只需打印“页面”即可生成分页链接

{{ pages }}

pagination.js >> 将此代码添加到 pagination.js 并将其导入您要使用分页的任何页面

class Pagination{

constructor(totalCount,currentPage,pageUri,perPage=2){
    this.perPage = perPage;
    this.totalCount =parseInt(totalCount);
    this.currentPage = parseInt(currentPage);
    this.previousPage = this.currentPage - 1;
    this.nextPage = this.currentPage + 1;
    this.pageCount = Math.ceil(this.totalCount / this.perPage);
    this.pageUri = pageUri;
    this.offset  = this.currentPage > 1 ? this.previousPage * this.perPage : 0;
    this.sidePages = 4;
    this.pages = false;
}



links(){
    this.pages='<ul class="pagination pagination-md">';

    if(this.previousPage > 0)
        this.pages+='<li class="page-item"><a class="page-link" href="'+this.pageUri + this.previousPage+'">Previous</a></li>';


        /*Add back links*/
        if(this.currentPage > 1){
            for (var x = this.currentPage - this.sidePages; x < this.currentPage; x++) {
                if(x > 0)
                    this.pages+='<li class="page-item"><a class="page-link" href="'+this.pageUri+x+'">'+x+'</a></li>';
            }
        }

        /*Show current page*/
        this.pages+='<li class="page-item active"><a class="page-link" href="'+this.pageUri+this.currentPage+'">'+this.currentPage+'</a></li>';

        /*Add more links*/
        for(x = this.nextPage; x <= this.pageCount; x++){

            this.pages+='<li class="page-item"><a class="page-link" href="'+this.pageUri+x+'">'+x+' </a></li>';

            if(x >= this.currentPage + this.sidePages)
                break;
        }


        /*Display next buttton navigation*/
        if(this.currentPage + 1 <= this.pageCount)
            this.pages+='<li class="page-item"><a class="page-link" href="'+this.pageUri+this.nextPage+'">Next</a></li>';

        this.pages+='</ul>';

    return this.pages;
}
}
module.exports = Pagination;