vascodogama

Думаю можно сделать вьюху, с чем то подобным(не знаю какая у вас субд)

Select 
   post_id, 
   sum(case when mood == 'positive' then 1 else 0 end) as count_positive,
   sum(case when mood == 'negative' then 1 else 0 end) as count_ negative
 FROM Reviews
 GROUP BY post_id

ну а потом как в статье

SELECT 
	widget_id, 
	((positive + 1.9208) / (positive + negative) - 
		1.96 * SQRT((positive * negative) / (positive + negative) + 0.9604) / 
 		(positive + negative)) / (1 + 3.8416 / (positive + negative)) 
 	AS ci_lower_bound 
	FROM widgets WHERE positive + negative > 0 
	ORDER BY ci_lower_bound DESC;