user: Question: What is Points Difference, when Points Against is 451?
Columns: ['Club', 'Played', 'Drawn', 'Lost', 'Points for', 'Points against', 'Points difference', 'Bonus Points', 'Points']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Club', 'Played', 'Drawn', 'Lost', 'Points for', 'Points against', 'Points difference', 'Bonus Points', 'Points']
SQL:

assistant: SELECT "Points difference" FROM "Table" WHERE "Points against" = '451';