user: Question: What is the oldest model porsche v12 that has points less than or equal to 0.
Columns: ['Year', 'Entrant', 'Chassis', 'Engine', 'Pts.']
Types: ['real', 'text', 'text', 'text', 'real']
Sample row: [1980.0, 'Shadow Cars', 'Shadow DN11', 'Ford Cosworth DFV V8', 0.0]
SQL:

assistant: SELECT MIN("Year") FROM "Table" WHERE "Engine" = 'porsche v12' AND "Pts." < 0.0;