Table: tv_episode
Columns: episode_no
title
directed_by
written_by
original_air_date
production_code

Question: What is the production code for the episode written by Drew Z. Greenberg?
SQL: SELECT "production_code" FROM tv_episode WHERE "written_by" = 'Drew Z. Greenberg'

Question: Who directed episode number 3?
SQL: SELECT "directed_by" FROM tv_episode WHERE "episode_no" = 3