user: Question: Which Date has a Tournament of BMW Open?
Columns: ['Outcome', 'Date', 'Tournament', 'Surface', 'Partner', 'Opponents', 'Score']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Winner', '15 June 1997', 'Gerry Weber Open', 'Grass', 'Michael Stich', 'David Adams Marius Barnard', '7–6, 6–3']
SQL:

assistant: SELECT "Date" FROM "Table" WHERE "Tournament" = 'BMW Open';