I think this should target category id:
-- [params]
-- int :category_id =
SELECT cr.target_id as post_id,
cr.model_used,
cr.classification->'negative' as negative,
cr.classification->'neutral' as neutral,
cr.classification->'positive' as positive
FROM classification_results cr
JOIN posts p ON p.id = cr.target_id
JOIN topics t ON t.id = p.topic_id
WHERE cr.model_used = 'sentiment'
AND t.category_id = :category_id
ORDER BY cr.id DESC
