user: Question: Who wrote episode that had 1.97 million u.s. viewers?
Columns: ['No. in series', 'No. in season', 'Title', 'Directed by', 'Written by', 'Original air date', 'Production code', 'U.S. viewers (million)']
Types: ['real', 'real', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: [105.0, 1.0, '"Exile on Main St."', 'Phil Sgriccia', 'Sera Gamble', 'September24,2010', '3X6052', '2.90']
SQL:

assistant: SELECT "Written by" FROM "Table" WHERE "U.S. viewers (million)" = '1.97';