why i can't use distinct instead of distinct on -
if i use distinct, i won't get duplicate *rows.* however, there are
content_items that are mapped to categories AND their
subcategories, with different weights and different push_dates,
pull_dates, etc. therefore, i'm obviously not going to have
duplicate rows, since i can end up with different distances and
mapping_weights for a given content_item.
i therefore need a way of eliminating duplicate content_ids in the
content_id column, not just eliminating duplicate rows.
(i hope that made more sense.) :)
