Table schema:
CREATE TABLE table_28138035_6 (womens_doubles VARCHAR, womens_singles VARCHAR, mens_singles VARCHAR)

Question: How many times did  li ju win the womens singles and wang liqin win the mens singles?
SQL: SELECT COUNT(womens_doubles) FROM table_28138035_6 WHERE womens_singles = "Li Ju" AND mens_singles = "Wang Liqin"