How to execute SQL statements in PrestaShop

prestashop_sql_commands.php

<?php
// SQL SELECT
// Simple SELECT
$sql = 'SELECT `id_authorization_role` FROM `' . _DB_PREFIX_ . 'authorization_role` t WHERE ' . implode(' OR ', $whereClauses);
// Or SELECT with INNER JOIN
$sql = 'SELECT * FROM ' . _DB_PREFIX_ . 'orders o
    INNER JOIN ' . _DB_PREFIX_ . 'order_detail od 
    ON o.id_order = od.id_order
    WHERE od.product_id = '. $var
);

$result = Db::getInstance()->executeS($sql);
foreach ($result as $row) {
    // do something
}

// SQL INSERT
$sql = 'INSERT IGNORE INTO `' . _DB_PREFIX_ . 'module_access` (`id_profile`, `id_authorization_role`) VALUES (' . (int) $idProfile . ',' . (int) $idRole . ')';

if (!Db::getInstance()->execute($sql)) {
    // failed
}

// SQL DELETE
$sql = 'DELETE FROM `' . _DB_PREFIX_ . 'access` WHERE `id_profile` = "' . $val . '"';

if (!Db::getInstance()->execute($sql)) {
    // failed
}

// SQL UPDATE
$sql = 'UPDATE `' . _DB_PREFIX_ . 'attribute` SET `id_attribute_group` = ' . (int) $this->id . ' WHERE `id_attribute` = ' . (int) $value['id'];

if (!Db::getInstance()->execute($sql)) {
    // failed
}