Get all WordPress category names and IDs

function show_category(){
global $wpdb;
$request = “SELECT $wpdb->terms.term_id, name FROM $wpdb->terms “;
$request .= ” LEFT JOIN $wpdb->term_taxonomy ON $wpdb->term_taxonomy.term_id = $wpdb->terms.term_id “;
$request .= ” WHERE $wpdb->term_taxonomy.taxonomy = ‘category’ “;
$request .= ” ORDER BY term_id asc”;
$categorys = $wpdb->get_results($request);
foreach ($categorys as $category) {
$output = ‘<span>’.$category->name.”(<em>”.$category->term_id.'</em>)</span>’;
echo $output;
}
}