Nodejs + Mysql + Return of Database Queries

Question

Good afternoon! I’m having some problems with NODEJS using a Mysql database, I’ve made several attempts and I’m not sure how to solve this problem. My problem is that I would like to consume the data return from a SELECT table in the back end but I’m not getting it. I can print the information on the screen using Insomnia (Postman) but I can’t bring the information to the backend and use it.

Query I am using to query in the database (note that in this layer I already do console.log but later will return 'Undefined')

Database settings (hidden but working correctly) and the function to execute the query, on this screen I ask to print in JSON information and it returns normal.

Feedback on the Front-End screen, ok

Console information.log I asked to print in the back end earlier, already returns me UNDEFINED

When I ask to print the variable 'res', just show me all this information

Well, I hope you can help me, thank you very much!

Answer 1

One model I use is the following

• connection.js:

---

const mysql = require("mysql");

const connection = mysql.createConnection({
  host: "localhost",
  port: "3306",
  database: "db",
  password: "senha",
  user: "root",
});

const query = (sql, callBack) => {
  return connection.query(sql, callBack);
};

module.exports = {
  connection,
  query,
};

• TodoController.js

---

const { query } = require("../connection");

module.exports = {
  get: function (req, res) {
    query("SELECT * FROM todos", function (error, result, field) {
      console.log(result); // resultado obtido
      if (error) {
        res.json(error);
      } else {
        res.json(result);
      }
    });
  },
};

• express:

---

var express = require("express");
var app = express();

const TodoController = require("./controllers/TodoController");

app.get("/", function (req, res) {
  res.send("Service Init ...");
});

app.get("/todo", TodoController.get);

app.listen(3000, function () {
  console.log("Service Web Port 3000!");
});

view the information also on the console, by the line placed inside the TodoController.js.

---

From what I could tell if you did the wrong part:

const teste = mysql.execSQLQuery("SELECT * FROM kit", res);
                                                       ^
                                                       |

passing the res and this may be going wrong because there is no variable response is a function that has the following parameters

function(error, result, field) { } 

and in that moment the problem, you have to follow the same function that you yourself stated in the images.