Table: doctor_who_audio_plays
Columns: series_sorted
title
doctor
featuring
released

Question: What was the date of release for the episode sorted value of 6Y/AA?
SQL: SELECT "released" FROM doctor_who_audio_plays WHERE "series_sorted" = '6y/aa'

Question: What is the series sorted value for the episode released December 2009?
SQL: SELECT "series_sorted" FROM doctor_who_audio_plays WHERE "released" = 'december 2009'