List child pages within page template

The ID of the current page is available via the global $post variable, so to get the ID use:

global $post;
$currentPage = $post->ID;

Then you can use $currentPage in your query 🙂

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)