user: Question: What year was there No competition in Mixed Doubles?
Columns: ['Year', "Men's singles", "Women's singles", "Men's doubles", "Women's doubles", 'Mixed doubles']
Types: ['text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['1991', 'Tamas Gebhard', 'Andrea Harsági', 'Tamas Gebhard Richard Banhidi', 'Andrea Dakó Andrea Harsági', 'Jeliazko Valkov Diana Filipova']
SQL:

assistant: SELECT "Year" FROM "Table" WHERE "Mixed doubles" = 'No competition';