CREATE TABLE table_15358729_6 (average_weekly_rank VARCHAR, average_nightly_rank VARCHAR)

How many were the show's average weekly ranking when it reached No. 2 in average nightly ranking?
SELECT COUNT(average_weekly_rank) FROM table_15358729_6 WHERE average_nightly_rank = "No. 2"
SELECT COUNT("average_weekly_rank") FROM "table_15358729_6" WHERE "No. 2" = "average_nightly_rank"