Develop Reference

Node + Mysql - Issue with connection

I do some mistake with connecting mysql in express which i couldn't figure out.
The basic connection code below works well.
var connection = mysql.createConnection({
host : 'localhost',
user:'root',
password:'',
database :'testdb'
});
connection.connect();
connection.query('SELECT * from test2table', function (err, data) {
if (err) throw err
console.log('The solution is: '+JSON.stringify(data)); -->could obtain data
});
But when it comes to use inside a get/post method , i donot get a response. Like code below:
var connection = mysql.createConnection({
host : 'localhost',
user:'root',
password:'',
database :'testdb'
});
connection.connect(function(err){
if(err) throw err;
console.log("connected");
});
app.get('/api/records',function(req,res){
connection.query('SELECT * from test2table', function (err, data) {
console.log(data);--> get blank response
});
});
Please let me know if i missed anything inbetween which affects. Thankyou.

Can you try with app.locals?
var connection = mysql.createConnection({
host : 'localhost',
user:'root',
password:'',
database :'testdb'
});
connection.connect(function(err){
if(err) throw err;
console.log("connected");
});
app.locals.connection = connection;
app.get('/api/records',function(req,res){
app.locals.connection.query('SELECT * from test2table', function (err, data) {
console.log(data);--> get blank response
});
});
See more details here: http://expressjs.com/en/api.html#app.locals

Passing Object with module exports

I am still new to nodejs and Javascript, I am sorry if my question appear to be very simple but I am struggling a lot and I can't seem to find an answer on the net.
What I want to do is basically calling a script (sqlRequest.js) and send an integer while calling it. This script will send an sql request to my database and will return the result (an object) to the original file.
Here are the codes:
router.post('/request', function(req, res, next){
var id = req.body.id;
var essai = require('./sqlRequest.js');
console.log("INDEX: "+essai.sendSQL(id)); });
And now the sqlRequest.js code:
exports.sendSQL = function(id) {
var mysql= require('mysql');
var connection = mysql.createConnection({
host : 'localhost',
user : 'bcombes',
password : 'bertrand1994',
database : 'totalkpi'
});
connection.connect();
var sql ="SELECT * FROM tra_ticket where id=?";
var insert=[id];
sql=mysql.format(sql, insert);
connection.query(sql, function(err, rows, fields) {
if (err) {
console.log('Error while performing Query.');
connection.end();
}
else {
connection.end();
console.log(rows);
return rows;
}
});};
On the console I can see that the console.log("INDEX: "+essai.sendSQL(id)); appears to be undefined and is displayed before the console.log(rows).
Is it possible that the server does not wait for the function to finish and display the variable anyway ?
Anyway thank you for taking the time to help.

Your logic to pass a variable between files is fine. The reason your seeing essai.sendSQL(id) return undefined is because connection.query(...) is called asynchronously and, as you've mentioned in your question, the console.log fires before the DB query completes.
To fix that issue you just need to refactor your code slightly:
var essai = require('./sqlRequest.js');
router.post('/request', function(req, res, next){
var id = req.body.id;
// send callback to sendSQL
essai.sendSQL(id, function(index) {
// this will only fire once the callback has been called
console.log("INDEX: " + index)
})
});
And then in sqlRequest.js:
exports.sendSQL = function (id, cb) {
var mysql = require('mysql');
var connection = mysql.createConnection({
host: 'localhost',
user: 'bcombes',
password: 'bertrand1994',
database: 'totalkpi'
});
connection.connect();
var sql = "SELECT * FROM tra_ticket where id=?";
var insert = [id];
sql = mysql.format(sql, insert);
connection.query(sql, function (err, rows, fields) {
if (err) {
console.log('Error while performing Query.');
connection.end();
}
else {
connection.end();
console.log(rows);
// call the callback
cb(rows);
}
});
};

MySQL DB Pool with Node.js and Restify

I am currently developing a node.js backend for a mobile app with potentially many users. However it's my first time in developing node.js. I was following a tutorial on how to connect to a mysql database via mysql pools.
I am able to create a single mysql connection and do queries via my routes.
The problem arises once I establish the file structure mentioned in the tutorial:
dbConnect
-[models]
--users.js
-db.js
-server-ks
I am not getting an error message regarding the connection of the mysql database - even if I enter a wrong password.
// server.js
///////////////////////////// basic setup ///////////////////////////////////
var restify = require('restify');
var bodyParser = require('body-parser');
var mysql = require('mysql');
var db = require('./db');
var users = require('./models/users');
///////////////////////////// initilisation of the server ///////////////////////////////////
var server = restify.createServer({
name: 'testUsers',
});
server.use(restify.bodyParser({ mapParams: true }));
///////////////////////////// Säuberung der URL //////////////////////////////////////////
server.pre(restify.pre.sanitizePath());
///////////////////////////// MySQL Instanz starten //////////////////////////////////////////
db.connect(db.MODE_PRODUCTION, function (err) {
if (err) {
console.log('Unable to connect to MySQL.')
process.exit(1)
} else {
server.listen(8080, function () {
console.log('Listening on port 8080 ...')
})
}
})
///////////////////////////// implementation of the routes ///////////////////////////////////
function send(req, res, next) {
var test = users.getAll();
res.json({ test: 'Hello ' + req.params.name });
return next();
};
My DB.js file looks the following:
var mysql = require('mysql'),
sync = require('async')
var PRODUCTION_DB = 'userDB',
TEST_DB = 'userDB'
exports.MODE_TEST = 'mode_test'
exports.MODE_PRODUCTION = 'mode_production'
var state = {
pool: null,
mode: null,
}
exports.connect = function (mode, done) {
state.pool = mysql.createPool({
connectionLimit: 50,
host: 'localhost',
user: 'user',
password: 'password',
database: 'userDB' // test
//mode === exports.MODE_PRODUCTION ? PRODUCTION_DB : TEST_DB
})
state.mode = mode
done()
}
exports.get = function () {
return state.pool
}
Could it be, that the tutorial spared out an essential part in utilizing mysql pools and node.js?
Thanks in advance for at least trying to answer that question.
Are there better methods sequelize(?) available to create performant connections to a MySQL database?

It looks like creating the pool object does not actually connect to the database. A big clue is that the createPool function is not asynchronous, which is what you would expect if it was actually connecting at that moment.
You have to make use of the returned pool object to perform a query, which IS asynchronous.
From the documentation:
var mysql = require('mysql');
var pool = mysql.createPool({
connectionLimit : 10,
host : 'example.org',
user : 'bob',
password : 'secret',
database : 'my_db'
});
pool.query('SELECT 1 + 1 AS solution', function(err, rows, fields) {
if (err) throw err;
console.log('The solution is: ', rows[0].solution);
});

Issue including js file in Node application

I want to create a manager to interact with mysql, but I'm not able to bring it into the main program. I'm mainly just trying to get the hang of javascript for this stuff (java, c background).
I have two files called main.js and MSYQLConnector.js. I want to use MYSQLConnector from
main.js
var root = __dirname, express = require('express');
var app = express();
var sql = require('./DBConnectors/MYSQLConnector.js');
var a = sql.sqlTest;//????? fail....
MYSQLConnector.js
var sqlTest = function (){
var mysql = require('mysql');
var connection = mysql.createConnection({
host : 'localhost',
user : 'root',
password : 'xxxx'
});
connection.connect();
connection.query('SELECT * from asset', function(err, rows, fields) {
if (err) throw err;
console.log('The solution is: ', rows[0].solution);
});
connection.end();
};
How can I do the import? Thanks

You need to export the function from your module. Add:
exports.sqlTest = sqlTest;
to the bottom of your MYSQLConnector.js file.
Also, see the nodejs api documentation for more details.

you're almost there, add "exports" in front of it:
exports.sqlTest = function (){
var mysql = require('mysql');
var connection = mysql.createConnection({
host : 'localhost',
user : 'root',
password : 'xxxx'
});
connection.connect();
connection.query('SELECT * from asset', function(err, rows, fields) {
if (err) throw err;
console.log('The solution is: ', rows[0].solution);
});
connection.end();
};

mySQL base authentication error in express framework

Recently I put my interest in node.js and learned a great about it and quickly move to the express framework. I've tried to connect my express application with mysql database and succeeded. Now I try to authenticate a simple login from connected with mysql database but I can't do that. Still don't get it why it is happening. Bellow here is the code I've used. A help will be greatly welcome.
var mysql = require('mysql');
connection = mysql.createConnection({
host: 'localhost',
user: 'root',
database: 'express_db',
password: '12345'
});
connection.connect();
exports.admin_login = function (req, res) {
res.render('./admin/login', {title: 'Please provide your credentials to login'});
};
exports.admin_home = function (req, res) {
var parse = req.body;
var name = parse.name;
var password = parse.password;
var sql = "select * from user where name = " + connection.escape(name) + " and password = " + connection.escape(password);
connection.query(sql, function (err, results) {
if (err) throw err;
if (name == results[0].name && password == results[0].password) {
req.session.regenerate(function () {
req.session.name = results[0].id;
res.render('./admin/home', {username: results[0].name});
});
}
});