Table: tv_episodes_15
Columns: series
season
title
directed_by
written_by
original_air_date
production_code
u_s_viewers_million

Question: What episode number of the series had a production code of bdf409?
SQL: SELECT MIN("series") FROM tv_episodes_15 WHERE "production_code" = 'BDF409'

Question: What episode number of the season was written by Tom Garrigus and had 2.31 million u.s. viewers?
SQL: SELECT MAX("season") FROM tv_episodes_15 WHERE "u_s_viewers_million" = '2.31' AND "written_by" = 'Tom Garrigus'

Question: What is the highest numbered episode in the series?
SQL: SELECT MAX("series") FROM tv_episodes_15

Question: What episode number in the series had a production code of bdf405?
SQL: SELECT MIN("series") FROM tv_episodes_15 WHERE "production_code" = 'BDF405'