user: Question: Who won the mixed doubles when Ji Xinpeng won the mens singles?
Columns: ['Year', 'Mens singles', 'Womens singles', 'Mens doubles', 'Womens doubles', 'Mixed doubles']
Types: ['real', 'text', 'text', 'text', 'text', 'text']
Sample row: [1984.0, 'Morten Frost', 'Zheng Yuli', 'Thomas Kihlström Stefan Karlsson', 'Karen Beckman Gillian Gilks', 'Martin Dew Gillian Gilks']
SQL:

assistant: SELECT "Mixed doubles" FROM "Table" WHERE "Mens singles" = 'Ji Xinpeng';