How to merge various MySQL queries results in a single JSON object - mysql

Question

I'm trying to write a REST API set in NodeJS to retrieve data from my MySQL database.
Here the code:
var express = require('express');
var mysql = require('mysql');
var app = express();
var connection = mysql.createConnection({
host : 'localhost',
user : 'root',
password : 'root',
database : 'apitest',
port : '3306',
multipleStatements: true
});
app.use(function(req, res, next) {
res.header("Access-Control-Allow-Origin", "*");
res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
next();
});
app.get('/users', function(req, res) {
connection.query('SELECT name, surname, address FROM users', function(err, results) {
if (err) throw err;
if (results) {
res.status(200).send(results);
};
});
});
app.get('/users/:userId', function (req, res) {
var userId = req.params.userId;
connection.query('SELECT * FROM users WHERE idUser = ?', [userId], function(err, result) {
if (err) throw err;
if (result) {
res.status(200).send(result);
};
});
});
app.get('/users/:userId/photos', function (req, res) {
var userId = req.params.userId;
connection.query('SELECT date, file, tags FROM photos WHERE idUser = ?', [userId], function(err, results) {
if (err) throw err;
if (results) {
res.status(200).send(JSON.stringify(results));
}
});
});
var server = app.listen(8080, function () {
var host = server.address().address;
var port = server.address().port;
console.log('Listening on http://%s:%s', host, port);
});
Everything goes well if I use the single REST call as written above.
The problem is that I want it to work differently, so when i call /users/:userId i want to retrieve user data and the relative photos in a single, well structured, JSON response.
Eg:
{
"name" : "John",
"surname" : "Doe",
"photos" : [
{
"date" : "2015-04-19T22:00:00.000Z",
"file" : "photo1.jpg",
"tags" : "holidays, 2015"
},
{
"date" : "2015-04-19T22:00:00.000Z",
"file" : "photo2.jpg",
"tags" : "holidays, 2015, nassau"
}
]
}
I've find a workaround by modifying the /users/:userId call as mentioned above:
app.get('/users/:userId', function (req, res) {
var userId = req.params.userId;
connection.query('SELECT * FROM users WHERE idUser = ?', [userId], function(err, results1) {
if (err) throw err;
if (results1) {
connection.query('SELECT date, file, tags FROM photos WHERE idUser = ?', [userId], function(err, results2) {
if (err) throw err;
if (results2) {
results1[0].photos = results2;
res.status(200).end(JSON.stringify(results1[0]));
}
});
}
});
});
Everything seems to go well but I think is not the right way because if i want to add more information from other tables in my object i would have to nest more and more functions...
Any suggestion?
Thanks in advance.

Answer 1

Check out Async, or any one of the popular promise libaries(when.js, Q.js, Bluebird).
In Async, it might look something like this.
var async = require('async');
app.get('/users/:userId', function (req, res) {
var userId = req.params.userId;
async.parallel({
user: function(callback){
connection.query('SELECT * FROM users WHERE idUser = ?', [userId], callback)
},
photos: function(callback){
connection.query('SELECT date, file, tags FROM photos WHERE idUser = ?', [userId], callback)
}
},
// Final callback, with all the results
function(err, results){
//results now has {user: ..., photos: ...}
var user = results.user;
user.photos = results.photos;
res.status(200).end(JSON.stringify(user));
});
});
Adding another call is as simple as adding another function inside parallel (or whatever it may be). The code is pretty similar for the promise libraries so I'll leave that as an exercise to you!
Let me know that this helped.