49 minutes ago, ThibaultWUN said:$idGroup = Db::getInstance()->executeS('SELECT id_group FROM `'._DB_PREFIX_.'group_lang` WHERE name LIKE 'mygroup' AND id_lang=5');
as per my understanding, mygroup should be in double quotes, so can you please try with below query:
$list = Db::getInstance()->executeS('SELECT id_customer FROM `'._DB_PREFIX_.'customer_group` WHERE id_group IN (SELECT id_group FROM `'._DB_PREFIX_.'group_lang` WHERE name LIKE "%MYGROUP%" AND id_lang=5)');
Let's give a try with this one and see what will be result..