user: Question: What was the airdate of episode number 18?
Columns: ['No. in series', 'No. in season', 'Title', 'Directed by', 'Written by', 'Original air date', 'U.S. viewers (millions)']
Types: ['real', 'real', 'text', 'text', 'text', 'text', 'text']
Sample row: [32.0, 1.0, '"A Death in the Family"', 'Mark Tinker', 'Shonda Rhimes , Jon Cowan & Robert Rovner', 'October1,2009', '11.58']
SQL:

assistant: SELECT "Original air date" FROM "Table" WHERE "No. in season" = 18.0;