user: Question: Who participated in the Mixed Doubles when Tracey Hallam participated in the Women's Singles?
Columns: ['Year', "Men's singles", "Women's singles", "Women's doubles", 'Mixed doubles']
Types: ['real', 'text', 'text', 'text', 'text']
Sample row: [1991.0, 'Hermawan Susanto', 'Susi Susanti', 'Kimiko Jinnai Hisako Mori', 'Thomas Lund Pernille Dupont']
SQL:

assistant: SELECT "Mixed doubles" FROM "Table" WHERE "Women's singles" = 'Tracey Hallam';