大家在做项目时肯定会遇到列表类的数据，如果在前台一下子展示，速度肯定很慢，那么我们可以分页展示，比如说100条数据，每10条一页，在需要的时候加载一页，这样速度肯定会变快了。
那么这里我给大家介绍如何在nodejs环境中用mysql实现分页。前面一些必要的配置我先不详细说了，这里主要说的是地址池的配置
// 数据库信息
var connection = mysql.createConnection({
host
: 'localhost',
port:3306,
user
: 'root',
password : '',
database : 'url',
multipleStatements: true //这里一定要加上这个。先别管什么用，一定要加上。
});

// 数据库信息
var connection = mysql.createConnection({
host
: 'localhost',
port:3306,
user
: 'root',
password : '',
database : 'url',
multipleStatements: true //这里一定要加上这个。先别管什么用，一定要加上。
});
因为我使用的是koa框架，所以用了async 、await 。这里不做理会，下面的代码才重要。
// 获取url
router.post('/csdnurl', async (ctx, next) => {

var start = (ctx.request.body.page - 1) * 10;

var sql = 'SELECT COUNT(*) FROM csdnurl ORDER BY id DESC; SELECT * FROM csdnurl ORDER BY id DESC limit ' + start + ',10';

let results = await query2(sql);

ctx.body = results
});

const query2 = function (sql) {

return new Promise((resolve, reject) => {

connection.query(sql, function (error, results) {

if (error) {

reject(error);

} else {

var allCount = results[0][0]['COUNT(*)'];

var allPage = parseInt(allCount) / 10;

var pageStr = allPage.toString();

if (pageStr.indexOf('.') > 0) {

allPage = parseInt(pageStr.split('.')[0]) + 1;

console.log(allPage)

}

var List = results[1];

resolve(List)

}

});

})
// 获取url
router.post('/csdnurl', async (ctx, next) => {

var start = (ctx.request.body.page - 1) * 10;

var sql = 'SELECT COUNT(*) FROM csdnurl ORDER BY id DESC; SELECT * FROM csdnurl ORDER BY id DESC limit ' + start + ',10';

let results = await query2(sql);

ctx.body = results
});

const query2 = function (sql) {

return new Promise((resolve, reject) => {

connection.query(sql, function (error, results) {

if (error) {

reject(error);

} else {

var allCount = results[0][0]['COUNT(*)'];

var allPage = parseInt(allCount) / 10;

var pageStr = allPage.toString();

if (pageStr.indexOf('.') > 0) {

allPage = parseInt(pageStr.split('.')[0]) + 1;

console.log(allPage)

}

var List = results[1];

resolve(List)

}

});

})1、ctx.request.body.page这里是前台传来的页数。2、 你可以看到sql语句有两条，哈哈，这里是关键了，在地址池配置multipleStatements: true就是这个原因，如果你不加，就会报错。3、ORDER BY id DESC 这是倒序的意思（根据id倒序）。4、 然后我使用await 异步操作封装了一个函数，是为了能够取到results值。当然你使用了express就不用考虑这一点，为啥会这样呢？如下：关于使用 koa路由与mysql模块， ctx.body获取不到值的问题关于使用 koa路由与mysql模块， ctx.body获取不到值的问题
var Koa = require('koa');
var Router = require('koa-router' );
var bodyParser = require('koa-bodyparser');
var mysql = require('mysql');
var app = new Koa();
var router = new Router();
app.use(bodyParser());

var connection = mysql.createConnection({
host
: 'localhost',
port:3306,
user
: 'root',
password : 'xxx',
database : 'url'
});
connection.connect();


//第一类封装 ，一般用于不传递多个参数
const query = function (sql) {

return new Promise((resolve, reject) => {

connection.query(sql, function (error, results) {

if(error){

reject(error);

}else{

resolve(results)

}

});

})
}
//第二类封装 ，一般用于传递多个参数
const query1 = function (userStr,name,passwd,token1) {

return new Promise((resolve, reject) => {

connection.query(userStr, function (error, result) {

if(error){

reject(error);

}else{

if (result.length > 0) {

json['message'] = '用户已经存在';

json['resultCode']= 1;

} else {

json['message'] = '注册成功';

json['token'] = token1;

json['resultCode'] = 200;

var insertStr = `insert into login (username, password,token) values ("${name}", "${passwd}","${token1}")`;

console.log(insertStr)

connection.query(insertStr, function (err, res) {

if (err) throw err;

})

}

resolve(json)

}

});

})
}


// 使用第一类封装
router.get( '/csdnurl', async(ctx, next) => {
var sql = "select * from csdnurl";

let results = await query(sql);

ctx.body=results
});
// 使用第一类封装
router.post('/login', async (ctx, next) => {

var name = ctx.request.body.username;

var passwd = ctx.request.body.password;

var userStr = `select username,password,token from login where username="${name}" and password="${passwd}"`;

let results = await query(userStr);

ctx.body = results
});

// 使用第二类封装
router.post('/register', async (ctx, next) => {

var name = ctx.request.body.username;

var passwd = ctx.request.body.password;

var token1 = jwt.sign({

username: name

}, secretkey, {

expiresIn: 60 * 8

});

var userStr = `select * from login where username="${name}"`;

let results = await query1(userStr,name,passwd,token1);

ctx.body = json
});
var Koa = require('koa');
var Router = require('koa-router' );
var bodyParser = require('koa-bodyparser');
var mysql = require('mysql');
var app = new Koa();
var router = new Router();
app.use(bodyParser());

var connection = mysql.createConnection({
host
: 'localhost',
port:3306,
user
: 'root',
password : 'xxx',
database : 'url'
});
connection.connect();


//第一类封装 ，一般用于不传递多个参数
const query = function (sql) {

return new Promise((resolve, reject) => {

connection.query(sql, function (error, results) {

if(error){

reject(error);

}else{

resolve(results)

}

});

})
}
//第二类封装 ，一般用于传递多个参数
const query1 = function (userStr,name,passwd,token1) {

return new Promise((resolve, reject) => {

connection.query(userStr, function (error, result) {

if(error){

reject(error);

}else{

if (result.length > 0) {

json['message'] = '用户已经存在';

json['resultCode']= 1;

} else {

json['message'] = '注册成功';

json['token'] = token1;

json['resultCode'] = 200;

var insertStr = `insert into login (username, password,token) values ("${name}", "${passwd}","${token1}")`;

console.log(insertStr)

connection.query(insertStr, function (err, res) {

if (err) throw err;

})

}

resolve(json)

}

});

})
}


// 使用第一类封装
router.get( '/csdnurl', async(ctx, next) => {
var sql = "select * from csdnurl";

let results = await query(sql);

ctx.body=results
});
// 使用第一类封装
router.post('/login', async (ctx, next) => {

var name = ctx.request.body.username;

var passwd = ctx.request.body.password;

var userStr = `select username,password,token from login where username="${name}" and password="${passwd}"`;

let results = await query(userStr);

ctx.body = results
});

// 使用第二类封装
router.post('/register', async (ctx, next) => {

var name = ctx.request.body.username;

var passwd = ctx.request.body.password;

var token1 = jwt.sign({

username: name

}, secretkey, {

expiresIn: 60 * 8

});

var userStr = `select * from login where username="${name}"`;

let results = await query1(userStr,name,passwd,token1);

ctx.body = json
});5、allPage是所有的页数，因为可能遇到小数的情况所以向下取整加一。6、resolve(List) 返回给前台数据