Table: ittf_pro_tour_winners_3
Columns: year_location
mens_singles
womens_singles
mens_doubles
womens_doubles

Question: Who was the womens double winner when the womens singles winner was Ding Ning?
SQL: SELECT "womens_doubles" FROM ittf_pro_tour_winners_3 WHERE "womens_singles" = 'Ding Ning'