user: Question: when the points for is 139 is points difference?
Columns: ['Club', 'Played', 'Won', 'Drawn', 'Lost', 'Points for', 'Points against', 'Points difference', 'Bonus Points', 'Points']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Club', 'Played', 'Won', 'Drawn', 'Lost', 'Points for', 'Points against', 'Points difference', 'Bonus Points', 'Points']
SQL:

assistant: SELECT "Points difference" FROM "Table" WHERE "Points for" = '139';