user: Question: what's the operational period with camp  Sajmište
Columns: ['Camp', 'Estimated deaths', 'Operational', 'Occupied territory', 'Current country of location', 'Primary means for mass killings']
Types: ['text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Auschwitz–Birkenau', '1,100,000', 'May 1940 – January 1945', 'Poland', 'Poland', 'Zyklon B gas chambers']
SQL:

assistant: SELECT "Operational" FROM "Table" WHERE "Camp" = 'Sajmište';