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How to create a loop for SELECT function, to keep data updated?

I'm using an Oracle database, and every time it updates, the server doesn't understand this update and needs me to drop it for it to update the data.
const express = require('express');
const oracledb = require('oracledb');
const app = express();
var cors = require('cors')
app.use (cors())
app.engine('html', require('ejs').renderFile);
app.set('view engine', 'html');
// Connection details for the Oracle database
const connectionString = 'dbprod';
const user = 'sapiensproducao';
const password = 'fabrica';
// Connect to the database
oracledb.getConnection(
{
connectionString: connectionString,
user: user,
password: password
},
function(err, connection) {
if (err) {
console.error(err.message);
return;
}
console.log('Connection was successful!');
// Execute a SQL query
const query = 'SELECT CODEMP,CODORI,NUMORP,SEQEOQ,DATREA,HORREA,CODPRO,CODDER,QTDRE1,QTDRFG,CODLOT,OBSEOQ from USU_VPROEXT ORDER BY DATREA DESC, HORREA DESC';
connection.execute(query, [], (err, result) => {
if (err) {
console.error(err.message);
return;
}
console.log('Query was successful!');
console.log()
// Render the HTML template and pass the query results as a local variable
app.get('/teste', (req, res) => {
res.json(result.rows)
});
});
}
);
app.listen(3000, () => {
console.log('Server is listening on port 3000');
});
I thought of creating a loop for this SELECT function, but how can I create it?
How can I keep running this select in a loop, to keep the data always updated?

In the structure of your web server, you only ever query the database once and then create an endpoint to serve that data. Instead, create an endpoint which queries the data whenever it's invoked. Which may look more like this:
// define the endpoint
app.get('/teste', (req, res) => {
// within the endpoint, query the database
oracledb.getConnection(
{
connectionString: connectionString,
user: user,
password: password
},
function(err, connection) {
if (err) {
console.error(err.message);
// DON'T DO THIS, return an actual response to the user
return;
}
console.log('Connection was successful!');
const query = 'SELECT CODEMP,CODORI,NUMORP,SEQEOQ,DATREA,HORREA,CODPRO,CODDER,QTDRE1,QTDRFG,CODLOT,OBSEOQ from USU_VPROEXT ORDER BY DATREA DESC, HORREA DESC';
connection.execute(query, [], (err, result) => {
if (err) {
console.error(err.message);
// DON'T DO THIS, return an actual response to the user
return;
}
console.log('Query was successful!');
console.log();
// return the results to the user
res.json(result.rows);
});
});
});
The key difference here is that instead of wrapping the endpoint in the query, you wrap the query in the endpoint. So every time the endpoint is invoked it re-queries the database.
Please also note the comments for your error handling. If you just return; from the function and never return a response to the client, the client will just hang until it times out. Return an actual response, which can include error codes, messages, anything you like. Even just res.json(false); would be better than no response at all.

nodejs mysql on pool connection Error: Connection lost: The server closed the connection

My question is similar to this post but the solution didnt work for me probably because im using a different type of mysql connection (pool). This is my code:
let config= {
host: '***',
user: 'admin',
password: '***,
port: '3306',
database: '***',
multipleStatements: true
};
const con = mysql.createPool(config);
select();
function select(){
return new Promise((resolve, reject) => {
con.getConnection(function (err, connection) {
if (err) throw err;
else
console.log("Connected!");
let sql = "SELECT * FROM bidPrice WHERE idExchangePlatform = 2;";
connection.query(sql, function (err, results, fields) {
connection.release();
connection.destroy();
if (err) throw err;
console.log(results)
resolve(results);
});
});
});
}
I also important to mention that im running this function using the following command
node --max-old-space-size=31744 index.js # Increase to 31 GB
This is because im working with millions of records from the database query
If i run this with regular node command i would be getting Javascript heap out of memory
When i tried integrating the solution i mentioned earlier to my code i just get a "killed" log after a while and then the process stops, should i handle server disconnect in a different way when using mysql.pool?

If you have big table with many rows, you will must check index for column 'idExchangePlatform' and create if doesn't make it
And simple variant your code:
function select(){
return new Promise((rs, rj) => {
let sql = "SELECT * FROM bidPrice WHERE idExchangePlatform = 2;";
pool.query(sql, (err, rows) => {
if(err)
return rj(err);
return rs(rows);
})
});
}

RESTful API access token mechanism

I'm developing a JavaScript/MySQL RESTful API for a business manager system using Express, Body-parser and MySQL. Currently, I am working on access tokens. Before any API call, the body must include an API key that is being verified by the API. In every API call function, I first check if the access token exists and if so, the API executes MySQL commands and sends back results.
The important thing is that I want to create a function that checks whether the access token exists and returns true or false. However, I can't figure out how to return this boolean value from the conn.query() method. Any help will be very much appreciated, I am desperate.
Here is my code:
function checkApiKey(apiKey) {
let sql = "SELECT * FROM apikeys WHERE apikey = '" + apiKey + "'";
conn.query(sql, (err, results) => {
if (err) throw err;
if (results.length > 0) return true;
return false;
});
}
app.get("/api/users",(req, res) => {
if (checkApiKey(req.body.apiKey)) {
let sql = "SELECT * FROM users";
let query = conn.query(sql, (err, results) => {
if (err) throw err;
res.send(results);
});
}
});
However, the checkApiKey() method returns undefined...

Your checkApiKey function returns undefined, because your logic returns true or false within sql's callback function.
I'd recommend another approach, using checkApiKey as middleware function:
const checkApiKey = (req, res, next) => {
conn.query("SELECT * FROM apikeys WHERE apikey = ?", [req.body.apiKey], (err, result) => {
if (err) throw err
if (results)
next() // continue to next router function
else
res.status(403).end('Unauthorized') // resolve with 403
})
}
app.get("/api/users",
checkApiKey, // middleware auth function
(req, res) => {
conn.query("SELECT * FROM users", (err, results) => {
if (err) throw err;
res.send(results)
})
})

Building a massive query based on single query [duplicate]

I'm using nodejs 10.26 + express 3.5 + node-mysql 2.1.1 +
MySQL-Server Version: 5.6.16.
I got 4 DELETE's and want only 1 Database Request, so i connected the DELETE commands with a ";"... but it fails always.
var sql_string = "DELETE FROM user_tables WHERE name = 'Testbase';";
sql_string += "DELETE FROM user_tables_structure WHERE parent_table_name = 'Testbase';";
sql_string += "DELETE FROM user_tables_rules WHERE parent_table_name = 'Testbase';";
sql_string += "DELETE FROM user_tables_columns WHERE parent_table_name = 'Testbase';";
connection.query(sql_string, function(err, rows, fields) {
if (err) throw err;
res.send('true');
});
It throws this error:
Error: ER_PARSE_ERROR: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'DELETE FROM user_tables_structure WHERE parent_table_name = 'Testbase';DELETE FR' at line 1
But if i paste this SQL in PhpMyAdmin it is always successful...
If i write it in single query's its succeed, too.
connection.query("DELETE FROM user_tables WHERE name = 'Testbase'", function(err, rows, fields) {
if (err) throw err;
connection.query("DELETE FROM user_tables_structure WHERE parent_table_name = 'Testbase'", function(err, rows, fields) {
if (err) throw err;
connection.query("DELETE FROM user_tables_rules WHERE parent_table_name = 'Testbase'", function(err, rows, fields) {
if (err) throw err;
connection.query("DELETE FROM user_tables_columns WHERE parent_table_name = 'Testbase'", function(err, rows, fields) {
if (err) throw err;
res.send('true');
});
});
});
});
Thanks for help!

I guess you are using node-mysql. (but should also work for node-mysql2)
The docs says:
Support for multiple statements is disabled for security reasons (it
allows for SQL injection attacks if values are not properly escaped).
Multiple statement queries
To use this feature you have to enable it for your connection:
var connection = mysql.createConnection({multipleStatements: true});
Once enabled, you can execute queries with multiple statements by separating each statement with a semi-colon ;. Result will be an array for each statement.
Example
connection.query('SELECT ?; SELECT ?', [1, 2], function(err, results) {
if (err) throw err;
// `results` is an array with one element for every statement in the query:
console.log(results[0]); // [{1: 1}]
console.log(results[1]); // [{2: 2}]
});
So if you have enabled the multipleStatements, your first code should work.

Using "multiplestatements: true" like shown below worked for me
var connection = mysql.createConnection({
host: 'localhost',
user: 'root',
password: '',
database: '',
multipleStatements: true
});
connection.connect();
var sql = "CREATE TABLE test(id INT DEFAULT 1, name VARCHAR(50));ALTER TABLE test ADD age VARCHAR(10);";
connection.query(sql, function(error, results, fields) {
if (error) {
throw error;
}
});

To Fetch Data from DB(SQL), the following function would work accurately
router.get('/', function messageFunction(req, res){
//res.send('Hi Dear Rasikh, Welcome to Test Page.') //=> One Way
dbConn.query('SELECT COUNT(name) as counted, name, last_name, phone, email from students',
function (err, rows, fields) { // another Way
if (err) throw err
dbConn.query('SELECT name, author from books',
function (err, rowsBook, fields) { // another Way
if (err) throw err
// console.log('The counted is: ', rows[0].counted); //=> Display in console
// res.send('Hi Dear Rasikh, Welcome to Test Page.'+ rows[0].counted) //=> Display in blank page
res.render('main/index',{data:rows, myData:rowsBook});
})
});
});

Accessing sqlite database which is password protected with the help of sqlcipher in javascript

I have followed this procedure, and have generate a database which is password protected with sqlcipher. Then I am making a connection by following sqlite3 syntax.
const sqlite3 = require('sqlite3').verbose();
const db = new sqlite3.Database('path/to/database/file', (err) => {
if (err) {
return console.error(err.message);
}
console.log('Connected to the in-memory SQlite database.');
});
var query = 'select COUNT(*) as count from table_name where column_name IS NOT NULL;';
db.serialize(function () {
db.all(query, function (err, rows) {
if (err) {
console.log(err);
}else{
console.log(rows);
}
});
});
My expectations were to get the query to be executed but getting error:
Error: SQLITE_NOTADB: file is not a database.
I tried but did not found any solution for this. Thanks in advance.

You need to supply the password you used for the encryption.
Use
pragma key='mypassword';
as your first statement, just after opening the database.
The whole idea of encrypted database is that you shouldn't be able to just "get the query to be executed", isnt't it?