user: Question: What was the surface where the outcome was Winner on 12 March 1989?
Columns: ['Outcome', 'Date', 'Tournament', 'Surface', 'Opponent in the final', 'Score in the final']
Types: ['text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Runner-up', '30 January 1984', 'Houston , USA WTA Virginia Slims', 'Carpet (I)', 'Hana Mandlíková', '4–6, 2–6']
SQL:

assistant: SELECT "Surface" FROM "Table" WHERE "Outcome" = 'Winner' AND "Date" = '12 March 1989';