user: Question: Who was the womens double winner when the womens singles winner was Ding Ning?
Columns: ['Year Location', 'Mens Singles', 'Womens Singles', 'Mens Doubles', 'Womens Doubles']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['2012 Velenje', 'Zhang Jike', 'Ding Ning', 'Ma Long Zhang Jike', 'Ding Ning Guo Yan']
SQL:

assistant: SELECT "Womens Doubles" FROM "Table" WHERE "Womens Singles" = 'Ding Ning';