user: Question: What is the attendance rate for the Middlesbrough opponent?
Columns: ['Date', 'Opponent', 'Venue', 'Result', 'Attendance']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['21 July 2006', 'Gainsborough Trinity', 'Away', 'Lost 2-1', 'Unknown']
SQL:

assistant: SELECT "Attendance" FROM "Table" WHERE "Opponent" = 'Middlesbrough';