How to stop sql query?

Question

MySQL

There is a code:

var sql = require("mysql");
var connection = sql.createConnection({
    host: 'localhost',
    user: 'root',
    password: 'password',
    database: 'chat'
});

app.get('/', function(req, res) {
    connection.connect();
    var loga = "kulonful";
    connection.query('select * from users where login = "'+loga+'"', function(err, result){
        if(err) { res.send('Произошла критическая ошибка'); }
        // здесь
        res.send(result);
    });
})

In the place "here" you need to stop the connection sql-query, otherwise the next time the script will give an error.
What is the function of stop?

Answer 1

Because connection.connect shouldn't be inside app.get, what do you think should happen if multiple users access your server at the same time? connection you have a global variable, each of the users will try to connect to it, although it is already connected and is processing another user's request at this time.
You either need to take out connect and make a connection as soon as the script starts, or use a connection pool and allocate connections from it to each user.