global $wpdb; // In case it\'s in a function...
$parent = 0; // Change to dig deeper in tree
$wpdb->query(
<<<SQL
    SELECT
        t1.`term_id`, /* The ID */
        t1.`name`, /* The name */
        t1.`slug`, /* The slug */
        t2.`parent`, /* The parent ID */
        t2.`count` /* The item Count */
    FROM
        {$wpdb->terms} AS t1,
        {$wpdb->term_taxonomy} AS t2
    WHERE
        (t1.`term_id` = t2.`term_id`) /* Join tables on term_id */
        AND (t2.`taxonomy` = \'category\') /* Make sure we get category taxonomy */
        /* Change parent (remove) according to your needs to dig deeper */
        AND (t2.`parent` = {$parent}) /* Remove to get all, not just top level */
        /* Remove the BINARY for case-insensitive comparison (both A and a) */
        AND (t1.`name` LIKE BINARY \'A%\');
SQL
);

当做