CREATE TABLE table_28138035_27 (mens_singles VARCHAR, womens_doubles VARCHAR)

Who is listed under mens singles when womens has wang nan zhang yining?
SELECT mens_singles FROM table_28138035_27 WHERE womens_doubles = "Wang Nan Zhang Yining"
SELECT "mens_singles" FROM "table_28138035_27" WHERE "Wang Nan Zhang Yining" = "womens_doubles"