user: Question: When US Open (2) is the championship what is the surface?
Columns: ['Outcome', 'Year', 'Championship', 'Surface', 'Partner', 'Opponents', 'Score']
Types: ['text', 'real', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Runner-up', 2003.0, 'US Open', 'Hard', 'Martina Navratilova', 'Virginia Ruano Pascual Paola Suárez', '6–2, 6–2']
SQL:

assistant: SELECT "Surface" FROM "Table" WHERE "Championship" = 'US Open (2)';