Do I need the promise in my MySQL statement? - mysql

Question

Below is a MySQL statement in my Node.js app. I used a promise in MySQL function to get API endpoint to work. Is this a typical pattern for Node.js and MySQL?
const express = require('express');
const app = express();
app.use(express.static('client'));
const config = require('./config')
var mysql = require('mysql');
var con = mysql.createConnection({
host: config.HOST,
user: config.USER,
password: config.PASSWORD,
database: config.DATABASE
});
function GetConsumers(req, res) {
return new Promise(function (resolve, reject) {
con.connect(function (err) {
if (err) throw err;
con.query("SELECT * FROM " + config.DATABASE + ".Contracts", function (err, result, fields) {
if (err) throw err;
//console.log(result);
resolve(result);
});
});
}).then(rows => res.send(rows));
}
app.get('/consumers', GetConsumers);
module.exports = app;

Answer 1

As George commented, you don't really need to return a promise here.
function GetConsumers(req, res) {
con.connect(function (err) {
if (err) {
res.send(err)
};
con.query("SELECT * FROM " + config.DATABASE + ".Contracts", function (err, result, fields) {
if (err) {
res.send(err)
};
//console.log(result);
res.send(result)
});
});
}
If you really want to use promises, it is always a good practice to catch the exceptions.
function GetConsumers(req, res) {
return new Promise(function (resolve, reject) {
con.connect(function (err) {
if (err){
reject(err);
}
con.query("SELECT * FROM " + config.DATABASE + ".Contracts",
function (err, result, fields) {
if (err){
reject(err);
}
//console.log(result);
resolve(result);
});
});
})
}
Call GetConsumers function where ever you want it.
GetConsumers(req,res).then(rows => res.send(rows))
}).catch(err =>{
console.log("Handle your error here");
res.send("error")
})
Mysql npm has good documentation of how to use the module. You can refer it more here