user: Question: How many margins have a winner of S. Singaravadivel?
Columns: ['Constituency', 'Winner', 'Party', 'Margin', 'Runner-up a', 'Party a']
Types: ['text', 'text', 'text', 'real', 'text', 'text']
Sample row: ['Madras North', 'D. Pandian', 'INC', 113771.0, 'N. V. N. Somu', 'DMK']
SQL:

assistant: SELECT COUNT("Margin") FROM "Table" WHERE "Winner" = 'S. Singaravadivel';