<?php
$deptID = "7";
$childCatID = $wpdb->get_col("SELECT term_id FROM $wpdb->term_taxonomy WHERE parent=$deptID");
if ($childCatID){
foreach ($childCatID as $kid)
{
$childCatName = $wpdb->get_row("SELECT name, term_id FROM $wpdb->terms WHERE term_id=$kid");
echo $childCatName->term_id;
echo $childCatName->name;
}
?>