SELECT tag, raw_tag
FROM
(SELECT
        raw_tag,
        COUNT (tag_id) as c_raw
FROM    tag
JOIN   object_tag
        ON (tag.id = object_tag.tag_id)
GROUP BY raw_tag
ORDER BY 2 DESC
) raw join
(SELECT
        tag,
        COUNT (tag_id) as c_tag
FROM    tag
JOIN   object_tag
        ON (tag.id = object_tag.tag_id)
GROUP BY tag
ORDER BY 2 DESC
) normal on (normal.tag=lower(raw.raw_tag))