user: Question: What is the average of the silver that has less than 0 gold
Columns: ['Rank', 'Nation', 'Gold', 'Silver', 'Bronze', 'Total']
Types: ['real', 'text', 'real', 'real', 'real', 'real']
Sample row: [1.0, 'Cuba', 4.0, 2.0, 3.0, 9.0]
SQL:

assistant: SELECT AVG("Silver") FROM "Table" WHERE "Gold" < 0.0;