How to redirect from a mysql query in node.js webapp?

I’m making a simple node.js webapp for inserting data into a database with a condition – when there’s two instances with the same time attribute, the insert query isn’t called and you get redirected to a simple html page with a message that you have to pick another time.

My question is, how can I redirect from a block of code belonging to query? or is there another way to let user know that he has to pick another time?

app.post('/', function(req, resp) {
    try {
        var name = req.body.name;
        var date = req.body.date + " " + req.body.time;
        var phone = req.body.phone;
        var spz = req.body.spz;
        var typeOfProblem = req.body.typeOfProblem;

        con.query(("SELECT COUNT(*) AS datecheck FROM `objednani` WHERE datetime = '"+ date +"'"), function(err, result){
            if (err) throw err;
            if(result[0].datecheck > 1){
                console.log("preplneno"); // THIS IS THE POINT WHERE I WANT TO REDIRECT THE USER
            } else {
                con.query(("INSERT INTO objednani (name, datetime, phone, spz, typeofproblem) " + "VALUES ('"+name+"','"+date+"','"+phone+"','"+spz+"','"+typeOfProblem+"')"), function (err, result) {
                    if (err) throw err;
                    console.log("uspech");
                });
            }
        });
    } catch (err) {
        resp.redirect('/fail');
    }
});

Answer

You can call resp.redirect('/fail'); inside your query block, or anywhere in function(req, resp) function. You don’t need to throw and catch.

As another suggestion: you can try parameter embedding for your sqls. otherwise you can be subject to sql injection attacks.