user: Question: How many episodes have been directed by David Duchovny?
Columns: ['No. in series', 'No. in season', 'Title', 'Directed by', 'Written by', 'Original air date']
Types: ['real', 'real', 'text', 'text', 'text', 'text']
Sample row: [13.0, 1.0, '"Slip of the Tongue"', 'David Duchovny', 'Tom Kapinos', 'September28,2008']
SQL:

assistant: SELECT COUNT("Title") FROM "Table" WHERE "Directed by" = 'David Duchovny';