wpdb get results doesn’t work with variable

Try it:

$search_by_input= $_POST["search_by_input"];
$client_id_by_nick_name = $wpdb->get_results( sprintf( "SELECT user_id FROM `%s` WHERE meta_value="%s";", $user_meta_table, $search_by_input ), ARRAY_A);

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