user: Question: What is the series number for the episode with production code BDF109?
Columns: ['Series #', 'Title', 'Directed by', 'Written by', 'Original air date', 'Production code', 'U.S. viewers (million)']
Types: ['real', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: [1.0, '"Pilot"', "Peter O'Fallon", 'Clifton Campbell', 'July11,2010', 'BDF179', '3.55']
SQL:

assistant: SELECT "Series #" FROM "Table" WHERE "Production code" = 'BDF109';