user: Question: List the competitor ranking with 900 defense points.
Columns: ['Seed', 'Rank', 'Player', 'Points', 'Points defending', 'Points won', 'New points', 'Status']
Types: ['real', 'real', 'text', 'real', 'text', 'real', 'real', 'text']
Sample row: [1.0, 1.0, 'Serena Williams', 8475.0, '500', 500.0, 8475.0, 'Quarterfinals lost to Samantha Stosur [7]']
SQL:

assistant: SELECT "Seed" FROM "Table" WHERE "Points defending" = '900';