user: Question: What is the lowest laps that has a manufacturer of Yamaha, and a time/retired of +1:08.312, and a grid less than 20?
Columns: ['Rider', 'Manufacturer', 'Laps', 'Time/Retired', 'Grid']
Types: ['text', 'text', 'real', 'text', 'real']
Sample row: ['Alex Barros', 'Honda', 30.0, '47:22.404', 2.0]
SQL:

assistant: SELECT MIN("Laps") FROM "Table" WHERE "Manufacturer" = 'Yamaha' AND "Time/Retired" = '+1:08.312' AND "Grid" < 20.0;