user: Question: Name the number  of weeks for San Francisco 49ers
Columns: ['Week', 'Date', 'Opponent', 'Result', 'Record', 'Game Site', 'Attendance']
Types: ['real', 'text', 'text', 'text', 'text', 'text', 'real']
Sample row: [1.0, 'September 15, 1963', 'New York Giants', 'L 28–37', '0–1', 'Memorial Stadium', 60029.0]
SQL:

assistant: SELECT COUNT("Week") FROM "Table" WHERE "Opponent" = 'San Francisco 49ers';