mysql query returns undefined in nodeJS

Question

This code returns an error because 'results(mysql.query)' returns undefined value. I have created a database table of 7~10 rows using mysql command shell and the database works perfectly from both workbench and command shell. is it because I have installed mysql in a wrong way? or code fault? I have tested the very same stuff in a different computer and it worked perfectly from there and suddenly it doesn't work. I didn't copy the file, just wrote/typed the same stuff from memory.

I have searched stackoverflow already and it seems everybody talks about async problem, which isn't really the one in my case.(same thing worked before)

used npm install mysql, mysql version is community 5.7

crudserver.js(main file)

const fs = require("fs"); //filesystem
const ejs = require("ejs");
const mysql = require("mysql");
const express = require("express"); //handles all the middlewares
const bodyParser = require("body-parser"); //handles "POST"

const client = mysql.createConnection({
  user:"****",
  password:"****",
  database:"testdb"
});

let app = express();
app.use(bodyParser.urlencoded({
  extended:false
}));

app.listen(52273, function(){
  console.log("server running at http://127.0.0.1:52273");
});

app.get("/",function (request,response){
  fs.readFile("crudlist.ejs","utf8",function(error,data){
    client.query("SELECT * FROM products", function(error,results){
      response.send(ejs.render(data,{
        data:results,
        mytitle:"title1",
        mytitlesub:"title2"
      }));
    });
  });
});

crudlist.ejs

 <% data.forEach(function (itm,index){ %>
 some codes....
 <% } >

and it says the 'data' is undefined.

Cannot read property 'forEach' of undefined at eval (eval at compile (F:\mycoding\node_modules\ejs\lib\ejs.js:549:12), :17:12) at returnedFn (F:\mycoding\node_modules\ejs\lib\ejs.js:580:17) at Object.exports.render (F:\mycoding\node_modules\ejs\lib\ejs.js:384:37) at Query._callback (F:\mycoding\crudserver.js:25:25) at Query.Sequence.end (F:\mycoding\node_modules\mysql\lib\protocol\sequences\Sequence.js:88:24) at F:\mycoding\node_modules\mysql\lib\protocol\Protocol.js:398:18 at Array.forEach (native) at F:\mycoding\node_modules\mysql\lib\protocol\Protocol.js:397:13 at _combinedTickCallback (internal/process/next_tick.js:73:7) at process._tickCallback (internal/process/next_tick.js:104:9)

Yury Fedorov · Accepted Answer · 2017-11-16 13:43:37Z

1

If data is undefined, you most likely have an error that you decided not to handle:

// note the first parameter of callback function - "error"
client.query("SELECT * FROM products", function(error,results){

You should test whether or not the error exists, and render the results only if it doesn't.

answered Nov 16, 2017 at 13:43

Yury Fedorov

15k6 gold badges56 silver badges70 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

Sungryeol Park Over a year ago

Thank you for your insight. the error contained this message: { Error: connect ECONNREFUSED 127.0.0.1:3306 at Object.exports._errnoException (util.js:1018:11) at exports._exceptionWithHostPort (util.js:1041:20) at TCPConnectWrap.afterConnect [as oncomplete] (net.js:1086:14) -------------------- at Protocol._enqueue (F:\mycoding\node_modules\mysql\lib\protocol\Protocol.js:145:48) at Protocol.handshake (F:\mycoding\node_modules\mysql\lib\protocol\Protocol.js:52:23) at Connection.connect (F:\mycoding\node_modules\mysql\lib\Connection.js:130:18)

Sungryeol Park Over a year ago

at Connection._implyConnect (F:\mycoding\node_modules\mysql\lib\Connection.js:461:10) at Connection.query (F:\mycoding\node_modules\mysql\lib\Connection.js:206:8) at F:\mycoding\crudserver.js:24:12 at tryToString (fs.js:456:3) at FSReqWrap.readFileAfterClose [as oncomplete] (fs.js:443:12) code: 'ECONNREFUSED', errno: 'ECONNREFUSED', syscall: 'connect', address: '127.0.0.1', port: 3306, fatal: true }

Yury Fedorov Over a year ago

For your question, it doesn't matter what the error is. It matters that you should handle it. As for this specific error, you don't have a mysql server listening on port 3306 on your localhost.

Sungryeol Park Over a year ago

it seems mysql connection is blocked by firewall or something. I'll be back with the fixed result.

Sungryeol Park · Accepted Answer · 2017-11-16 15:00:50Z

0

problem solved: reinstalled mySQL. setup port to default 3306. I did set up my port to some custom numbers when I was installing, and it was the real cause of the problem. do not change port number from 3306 unless it is necessary.

answered Nov 16, 2017 at 15:00

Sungryeol Park

1755 silver badges12 bronze badges

Collectives™ on Stack Overflow

mysql query returns undefined in nodeJS

2 Answers 2

4 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

4 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related