user: Question: What is the year when Sigourney Weaver was nominated for Best Actress?
Columns: ['Year (Ceremony)', 'Actor/Actress', 'Category', 'Film title used in nomination', 'Result']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['1938 (11th)', 'Fay Bainter', 'Best Actress', 'White Banners', 'Nominee']
SQL:

assistant: SELECT "Year (Ceremony)" FROM "Table" WHERE "Category" = 'Best Actress' AND "Actor/Actress" = 'Sigourney Weaver';