-- taken from
-- http://vrypan.net/log/archives/2005/03/10/migrating-from-drupal-to-wordpress/
-- and then improved :-) 

-- these lines will result in the deletion of all existing posts, comments
-- and categories. Comments these out using '--' or /* ... */ if you don't
-- want that to happen 
DELETE FROM wp_categories ;
DELETE FROM wp_posts ;
DELETE FROM wp_post2cat ;
DELETE FROM wp_comments ;

/*
-- does not work (think it is to do with password issues)
-- also causes problems with auto-increment
delete from wp_users;

INSERT INTO wp_users
  (ID, user_login, user_pass, user_nickname, user_email, user_registered)
  SELECT
  uid, name, pass, name, mail, FROM_UNIXTIME(timestamp)
  FROM users;
*/

INSERT into wp_categories(
  cat_ID,cat_name, category_nicename, category_description, category_parent
  )
  SELECT term_data.tid, name, name, description, parent
  FROM term_data, term_hierarchy
  WHERE term_data.tid=term_hierarchy.tid;

INSERT INTO wp_posts(
  ID, post_author, post_date, post_content, post_title, post_excerpt,
  post_name, post_modified
  )
  SELECT a.nid, 1, FROM_UNIXTIME(a.created), b.body, a.title, b.teaser, concat('OLD',a.nid), FROM_UNIXTIME(a.changed)
  FROM node as a, node_revisions as b
  WHERE a.nid = b.nid AND (a.type='blog' OR a.type='page' OR a.type='story' OR a.type='forum');

INSERT INTO wp_post2cat (post_id,category_id)
  SELECT nid,tid
  FROM term_node ;

INSERT INTO wp_comments (
  comment_post_ID, comment_date, comment_content, comment_parent
  )
  SELECT nid, FROM_UNIXTIME(timestamp), concat(subject,' ', comment), thread
  FROM comments ;

DROP TABLE term_data;
DROP TABLE term_hierarchy;
DROP TABLE node;
DROP TABLE term_node;
DROP TABLE comments;
DROP TABLE users;