user: Question: What is the race 12 Hours in length?
Columns: ['Race', 'Length', 'Class', 'Circuit', 'Date']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['24 Hour Pepsi Challenge', '24 Hours', 'All', 'Daytona International Speedway', 'February 5 February 6']
SQL:

assistant: SELECT COUNT("Race") FROM "Table" WHERE "Length" = '12 Hours';