user: Question: what rank has viewers at 6.45?
Columns: ['#', 'Episode', 'Rating', 'Share', 'Rating/Share (18-49)', 'Viewers (millions)', 'Rank (Timeslot)', 'Rank (Night)', 'Rank (Week)']
Types: ['real', 'text', 'text', 'real', 'text', 'text', 'text', 'text', 'text']
Sample row: [1.0, '"Faith"', '7.3', 12.0, '4.2/12', '11.83', '1', '3', '10']
SQL:

assistant: SELECT "Rank (Week)" FROM "Table" WHERE "Viewers (millions)" = '6.45';