user: Question: List the number of active years for Attaquant.
Columns: ['Name', 'Position', 'Period', 'Appearances¹', 'Goals¹', 'Nationality²']
Types: ['text', 'text', 'text', 'real', 'real', 'text']
Sample row: ["David N'Gog", 'Forward', '2006 – 2008', 25.0, 3.0, 'France']
SQL:

assistant: SELECT "Period" FROM "Table" WHERE "Position" = 'Attaquant';