Get data from MySQL query for use in nodejs

Question

Trying to query my database and each time I do, it runs all the queries at the end instead of when I need them in nodejs.

var mysql = require('mysql');

var con = mysql.createConnection({
  host: database.host,
  user: database.user,
  password: database.password,
  database: database.database
});

The connection data I am pulling from a json file.

function getSymbol(id){
var s = "";
con.query("SELECT * FROM Symbol WHERE PlayerID = '" + id + "'", function (err, result, fields) {
    if (err) throw err;
    console.log(result);
    if (result.length < 1) {
        console.log(result);
        s = result[0].Symbol;
    }
    else {
        s = "!";
    }
});
console.log(s);
return s;

}

It all runs at the end of the program wondering if there is a fix or if I should switch to python (seriously considering rewriting all of it at this point).

GRS · Accepted Answer · 2020-01-09 15:10:33Z

1

The problem is what you have written comes under NIO and it wont wait for executing the next statement unless you ask it to. Try the below code:

async function getSymbol(id){
   var s = "";
   try {
    let result = await con.query("SELECT * FROM Symbol WHERE PlayerID = '" + id + "'")
    if (result.length < 1) {
        console.log(result);
        s = result[0].Symbol;
    }
    else {
        s = "!";
    }
   }catch(error){
        console.log(error);
        throw new error;
   }
    console.log(s);
   return s;
 }

Note: I have used async/await. You can also use Promises

answered Jan 9, 2020 at 15:10

GRS

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5 Comments

wig on the run Over a year ago

Ok it now returns [object Promise] instead of nothing to the method call on a console.log, and then after the log it runs the query. Do I also need to migrate the other stuff to a async method and run the return with await.

GRS Over a year ago

what is your console.log(s) is printing?

wig on the run Over a year ago

It was returning ! instead of what I have it set to in my database ?.

GRS Over a year ago

Can you try changing the query to - "select * from Symbol" and you are getting some result?

wig on the run Over a year ago

I found the issue it was my if case it was wanting less then 1 instead of 1 and now it works, so your original solution was the correct one I just did a dumb. Thank you for the assistance.

Vetras · Accepted Answer · 2020-01-09 15:18:08Z

0

As mentioned, the method is NOT sync. Your result will be on the callback you pass.

con.query(sql, function (err, result) {
    if (err) throw err;
    console.log("The Data: " + result);
});

More Info: https://www.w3schools.com/nodejs/nodejs_mysql.asp

Moreover, you need to connect first with con.connect( <callback-here> ).

The best way to work with this is to avoid the callbacks for async/wait syntax.

answered Jan 9, 2020 at 15:18

Vetras

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