How to check if the email already exists in database - mysql

Question

i am trying to put email validation if the user is already registered
but the values are always inserted in my database even when the email already exists in database.
router.get('/save',function(req,res){
var uname = req.query.username;
var em = req.query.email;
var passw = req.query.pass;
var gender = req.query.gender;
var dob = req.query.date;
var con = mysql.createConnection({
host:"localhost",
user:"root",
password:"",
database:"sherrydb"
});
con.query('select * from loginn where email= "'+req.query.email+'" ',function(err,row){
if(err){
con.query('insert into loginn(name, password, email, gender, date) VALUES("' + uname + '","' + passw + '","' + em + '","' + gender + '","' + dob + '")',
function(err,rows,fields){
console.log(rows);
res.send("inserted");
});
}
else{
alert("user already registered");
return;
}
});
con.end();
});

Answer 1

You're only inserting when there is an error and your database query won't throw any error for both the cases, if it will not find any results or if it will find any results.
What will be in the results of those database queries -
When database has entry for that email will return array of rows containing that email.
when database doesn't have entry with that email it will return an empty array.
So, What you can do is, check for the query result length, if result length is 0 then you can insert and if greater than 0. You should send response of "Already Registered" or something.

Answer 2

router.get('/save',function(req,res){
var uname = req.query.username;
var em = req.query.email;
var passw = req.query.pass;
var gender = req.query.gender;
var dob = req.query.date;
var con = mysql.createConnection({
host:"localhost",
user:"root",
password:"",
database:"sherrydb"
});
con.query('select * from loginn where email="'+em+'" ', (err, result) => {
if (err) throw err;
if (result.length>0){
res.send("user already registered");
}
else{
var conn = mysql.createConnection({
host:"localhost",
user:"root",
password:"",
database:"sherrydb"
});
conn.query('insert into loginn(name, password, email, gender, date) VALUES("' + uname + '","' + passw + '","' + em + '","' + gender + '","' + dob + '")',function(err,rows,fields){
console.log(rows);
res.send("inserted");
});
conn.end();
}
});
con.end();
});