NodeJS app fails to run queries on MySQL database more than 6 times

Question

I'm hosting a web app on localhost:3000 via NodeJS (with MySQL database via WAMP). Front end has a button to insert a record into a MySQL database table (called tblbacktrack). It runs the query as expected exactly 6 times, then stops working altogether, without an error or crash. 6 times, every time. If I change the query to a delete, same problem: 6 deletions is all I get until I refresh the page via the browser.

App2.js:

const express = require('express');
const mysql = require('mysql');
const multer = require('multer');
const upload = multer({ dest: 'uploads/' });

// create connection
const db = mysql.createConnection({
    host: 'localhost', 
    user: 'root',
    password: '',
    database: 'journey_test'
})

 // connect to mysql
 db.connect(err => {
     if(err) {
         throw err
     }
     console.log('MySQL Connected');
 })

 const app = express()

 app.use(express.static('public'));
 app.set('view engine', 'ejs');
         

// This pulls index.ejs to the root folder location of the site.
app.get('/', function (req, res) {
    res.render('index2');
});


app.post('/deleteBtDb/', upload.none(), function (req, res, next) { 
    // let sql = `DELETE from tblbacktrack limit 1`
    let sql = `INSERT into tblbacktrack (btEntryNum, btDate) values ('E: 19810809', '2021-05-05');`
    let query = db.query(sql, (err, results) => {
            if(err) {
                    throw err
                }
        })
})

// Let the console know that the server has started on port 3000
 app.listen('3000', () => {
     console.log('Server Started on port 3000')
 })

index2.ejs:

<!DOCTYPE html>
  <html>
    <head>
    <link href="/css/style.css" rel="stylesheet" type="text/css" media="all" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0"> 
    <meta http-equiv="content-type" content="text/html; charset=utf-8" />
 </head>
 <body>
    <div class="container">
        <div class="Header">
        </div>
        <div class="Footer"></div>
        <div class="Middle">
          <div id="Middle-Center" class="Middle-Center"></div>
          <div id="Middle-Left" class="Middle-Left"></div>
          <div id="Middle-Right" class="Middle-Right"><%- include ('../views/middle-right'); %></div>
        </div>
    </div>     
</body>

Middle-right.ejs:

    <div><button onclick="deleteBtDb()">Click me</button></div>
    <script>
    function deleteBtDb() {
        var xhttp = new XMLHttpRequest();
        xhttp.open("POST", "./deleteBtDb/", true);
        xhttp.send();
         }
    </script>

If I run the same queries in phpMyAdmin, they work, and I can definitely run them successfully more than 6 times there. If I set up a for loop in app2.js, such that a single click of the index2.ejs button should insert 10 new records, it successfully inserts 10 new records. Please help! I don't know how to further troubleshoot this.

what error it gives nodejs when it doesnt work ? (after 6 times) — Stefani Toto
– Stefani Toto, Commented Sep 8, 2021 at 23:14
No error in NodeJS. Just stops having results. Visual Studio Code terminal doesn't come up with anything new to tell me. [nodemon] starting node app2.js Server Started on port 3000 MySQL Connected — Mervius
– Mervius, Commented Sep 8, 2021 at 23:30

Mervius · Accepted Answer · 2021-09-09 01:39:36Z

1

Solved it!

I wasn't using a "res" object in there. Added "res.status(201).json()", and it's all better now.

app.post('/deleteBtDb/', upload.none(), function (req, res, next) { 
    let sql = `DELETE from tblbacktrack order by btID ASC limit 1`
    let query = db.query(sql, (err, results) => {
        if(err) {
           throw err
           }
        })
res.status(201).json();
})

answered Sep 9, 2021 at 1:39

Mervius

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