Chaining Promises In Loop - node.js

Question

I am struggling to loop through the array periods whilst querying the DB and inserting data. The problem I am facing can be seen on the 5th from last line. The final db.queryPromise does not get invoked.
Please see comment 5 lines from the bottom for where the problem is.
// db.js
const mysql = require('mysql');
const connection = mysql.createConnection({
host : 'localhost',
user : ****,
password : ****,
database : ****,
});
module.exports = connection;
module.exports.queryPromise = function (args) {
return new Promise((resolve, reject) => {
connection.query(args, (err, rows, fields) => {
if (err) return reject(err);
resolve(rows);
});
});
};
module.exports.connectPromise = new Promise((resolve, reject) => {
connection.connect(err => {
if (err) reject(err);
resolve();
});
});
// app.js
const db = require('../config/db');
const periods = ['1h','12h','24h','1w','1m','3m','1y','all'];
const sqlCarIds = `SELECT id FROM car_models ORDER BY id DESC LIMIT 200;`;
return db.queryPromise(sqlCarIds)
.then((rows) => {
const car_ids = [];
for (let i = rows.length - 1; i >= 0; i--) {
car_ids.push(rows[i].car_id);
};
for (let i = periods.length - 1; i >= 0; i--) {
const sqlSnapshot = `SELECT price FROM car_models;`;
db.queryPromise(sqlSnapshot)
.then(([row]) => {
if (!row) {
throw new Error('API call found nothin');
}
const highPrice = row.high;
const sqlInsert = `INSERT into price_cache (high) VALUES (` + highPrice` + )`;`
console.log(sqlInsert); // logs correctly formed query
db.queryPromise(sqlInsert)
.then(() => {
console.log('this should fire'); // doesn't fire
});
});
}
});

Answer 1

The SQL syntax for the sqlInsert is invalid. You will need to write it like following example. You need to use the ${expression} literals to add the value of an expression into a "Template String". Your promise doesn't get resolved because there is an error which rejects it.
const sqlInsert = `INSERT into price_cache (high) VALUES (${highPrice})`;