text: 
  select count(*) from tag, site, question, tag_question
  where
  site.site_name='superuser' and
  tag.name='oem' and
  tag.site_id = site.site_id and
  question.site_id = site.site_id and
  tag_question.site_id = site.site_id and
  tag_question.question_id = question.id and
  tag_question.tag_id = tag.id
  