user: Question: At what tournament did Pete Sampras begin his lead?
Columns: ['Years led', 'Span of years led', 'Player', 'Titles won at point of lead', 'Total Career titles', 'Tournament at which lead began']
Types: ['text', 'real', 'text', 'real', 'real', 'text']
Sample row: ['1877–1880', 4.0, 'Spencer Gore', 1.0, 1.0, 'Wimbledon']
SQL:

assistant: SELECT "Tournament at which lead began" FROM "Table" WHERE "Player" = 'Pete Sampras';