user: Question: How many Gold for the Nation in Rank 15 with 0 Silver?
Columns: ['Rank', 'Nation', 'Gold', 'Silver', 'Bronze', 'Total']
Types: ['text', 'text', 'real', 'real', 'real', 'real']
Sample row: ['1', 'South Korea', 7.0, 3.0, 2.0, 12.0]
SQL:

assistant: SELECT SUM("Gold") FROM "Table" WHERE "Rank" = '15' AND "Silver" > 0.0;