user: Question: How many date of successor seated is New Jersey 2nd in the district?
Columns: ['District', 'Vacator', 'Reason for change', 'Successor', 'Date successor seated']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['Georgia 3rd', 'Vacant', 'Rep-elect Washington Poe declined the seat', 'George W. Towns ( D )', 'Seated January 5, 1846']
SQL:

assistant: SELECT COUNT("Date successor seated") FROM "Table" WHERE "District" = 'New Jersey 2nd';