Problems with count_by_sql method

@numRows = count_by_sql("SELECT COUNT(DISTINCT Opinions.id), SUM
(Ratings.score) as score_sum FROM Opinions
LEFT JOIN Ratings ON Opinions.id =
Ratings.opinion_id WHERE score_sum > 20")

Will return us the SUM of COUNT(DISTINCT Opinions.id) AND SUM
(Ratings.score).
But we only need the value of COUNT(DISTINCT Opinions.id)

Is there a way to achieve that in rails?